Split GoogleUtilities from FirebaseCore (#1370)

60 files changed, 1541 insertions, 817 deletions

diff --git a/.travis.yml b/.travis.yml
index dea83ed..79903c7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -52,50 +52,60 @@ jobs:
     - stage: test
       env:
         - PROJECT=Firebase PLATFORM=iOS METHOD=pod-lib-lint
+        # Set ALT_SOURCES like the following to continue lint testing until release when Utilities
+        # or Core APIs change. GoogleUtilities.podspec and FirebaseCore.podspec should be
+        # manually pushed to a temporary Specs repo. See
+        # https://guides.cocoapods.org/making/private-cocoapods.
+        # ALT_SOURCES="--sources=git@github.com:paulb777/Specs.git,https://github.com/CocoaPods/Specs.git"
+        - ALT_SOURCES="--sources=https://github.com/paulb777/Specs.git,https://github.com/CocoaPods/Specs.git"
       before_install:
         - ./scripts/if_changed.sh ./scripts/install_prereqs.sh
       script:
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseCore.podspec
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseAuth.podspec
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseDatabase.podspec
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseMessaging.podspec
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseStorage.podspec
-        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseFunctions.podspec
+        - ./scripts/if_changed.sh bundle exec pod lib lint GoogleUtilities.podspec
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseCore.podspec $ALT_SOURCES
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseAuth.podspec $ALT_SOURCES
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseDatabase.podspec $ALT_SOURCES
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseMessaging.podspec $ALT_SOURCES
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseStorage.podspec $ALT_SOURCES
+        - ./scripts/if_changed.sh bundle exec pod lib lint FirebaseFunctions.podspec $ALT_SOURCES
 
     - stage: test
       env:
         - PROJECT=Firestore PLATFORM=iOS METHOD=pod-lib-lint
+        - ALT_SOURCES="--sources=https://github.com/paulb777/Specs.git,https://github.com/CocoaPods/Specs.git"
       before_install:
         - ./scripts/if_changed.sh ./scripts/install_prereqs.sh
       script:
         # Eliminate the one warning from BoringSSL when CocoaPods 1.6.0 is available.
         # The travis_wait is necessary because the command takes more than 10 minutes.
-        - travis_wait ./scripts/if_changed.sh bundle exec pod lib lint FirebaseFirestore.podspec --allow-warnings --no-subspecs
+        - travis_wait ./scripts/if_changed.sh bundle exec pod lib lint FirebaseFirestore.podspec --allow-warnings --no-subspecs $ALT_SOURCES
 
     # pod lib lint to check build and warnings for static library build - only on cron jobs
     - stage: test
       env:
         - PROJECT=Firebase PLATFORM=iOS METHOD=pod-lib-lint
+        - ALT_SOURCES="--sources=https://github.com/paulb777/Specs.git,https://github.com/CocoaPods/Specs.git"
       before_install:
         - ./scripts/if_cron.sh ./scripts/install_prereqs.sh
       script:
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseCore.podspec --use-libraries
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseAuth.podspec --use-libraries
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseDatabase.podspec --use-libraries
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseCore.podspec --use-libraries $ALT_SOURCES
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseAuth.podspec --use-libraries $ALT_SOURCES
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseDatabase.podspec --use-libraries $ALT_SOURCES
         # The Protobuf dependency of FirebaseMessaging has warnings with --use-libraries
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseMessaging.podspec --use-libraries --allow-warnings
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseStorage.podspec --use-libraries
-        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseFunctions.podspec --use-libraries
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseMessaging.podspec --use-libraries --allow-warnings $ALT_SOURCES
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseStorage.podspec --use-libraries $ALT_SOURCES
+        - ./scripts/if_cron.sh bundle exec pod lib lint FirebaseFunctions.podspec --use-libraries $ALT_SOURCES
 
     - stage: test
       env:
         - PROJECT=Firestore PLATFORM=iOS METHOD=pod-lib-lint
+        - ALT_SOURCES="--sources=https://github.com/paulb777/Specs.git,https://github.com/CocoaPods/Specs.git"
       before_install:
         - ./scripts/if_cron.sh ./scripts/install_prereqs.sh
       script:
         # TBD - non-portable path warnings
         # The travis_wait is necessary because the command takes more than 10 minutes.
-        - travis_wait ./scripts/if_cron.sh bundle exec pod lib lint FirebaseFirestore.podspec --use-libraries --allow-warnings --no-subspecs
+        - travis_wait ./scripts/if_cron.sh bundle exec pod lib lint FirebaseFirestore.podspec --use-libraries --allow-warnings --no-subspecs $ALT_SOURCES
 
     # Alternative platforms
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a935c4d..10d8ce2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -50,6 +50,7 @@ enable_testing()
 # These are ordered by a topological sort on DEPENDS attributes. This is
 # required because CMake fails the build if you have a DEPENDS on a target that
 # does not exist yet.
+include(external/GoogleUtilities)
 include(external/FirebaseCore)
 include(external/googletest)
 include(external/zlib)
diff --git a/Example/Core/Tests/FIRAppEnvironmentUtilTest.m b/Example/Core/Tests/FIRAppEnvironmentUtilTest.m
index 2469e8d..4ac2ef5 100644
--- a/Example/Core/Tests/FIRAppEnvironmentUtilTest.m
+++ b/Example/Core/Tests/FIRAppEnvironmentUtilTest.m
@@ -15,17 +15,17 @@
 #import <Foundation/Foundation.h>
 #import <XCTest/XCTest.h>
 
-#import <FirebaseCore/FIRAppEnvironmentUtil.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
 
 #import "FIRTestCase.h"
 
-@interface FIRAppEnvironmentUtilTest : FIRTestCase
+@interface GULAppEnvironmentUtilTest : FIRTestCase
 
 @property(nonatomic) id processInfoMock;
 
 @end
 
-@implementation FIRAppEnvironmentUtilTest
+@implementation GULAppEnvironmentUtilTest
 
 - (void)setUp {
   [super setUp];
@@ -43,21 +43,21 @@
   NSOperatingSystemVersion osTen = {.majorVersion = 10, .minorVersion = 0, .patchVersion = 0};
   OCMStub([self.processInfoMock operatingSystemVersion]).andReturn(osTen);
 
-  XCTAssertTrue([[FIRAppEnvironmentUtil systemVersion] isEqualToString:@"10.0"]);
+  XCTAssertTrue([[GULAppEnvironmentUtil systemVersion] isEqualToString:@"10.0"]);
 }
 
 - (void)testSystemVersionInfoMajorMinor {
   NSOperatingSystemVersion osTenTwo = {.majorVersion = 10, .minorVersion = 2, .patchVersion = 0};
   OCMStub([self.processInfoMock operatingSystemVersion]).andReturn(osTenTwo);
 
-  XCTAssertTrue([[FIRAppEnvironmentUtil systemVersion] isEqualToString:@"10.2"]);
+  XCTAssertTrue([[GULAppEnvironmentUtil systemVersion] isEqualToString:@"10.2"]);
 }
 
 - (void)testSystemVersionInfoMajorMinorPatch {
   NSOperatingSystemVersion osTenTwoOne = {.majorVersion = 10, .minorVersion = 2, .patchVersion = 1};
   OCMStub([self.processInfoMock operatingSystemVersion]).andReturn(osTenTwoOne);
 
-  XCTAssertTrue([[FIRAppEnvironmentUtil systemVersion] isEqualToString:@"10.2.1"]);
+  XCTAssertTrue([[GULAppEnvironmentUtil systemVersion] isEqualToString:@"10.2.1"]);
 }
 
 @end
diff --git a/Example/Core/Tests/FIRLoggerTest.m b/Example/Core/Tests/FIRLoggerTest.m
index b871244..f179bde 100644
--- a/Example/Core/Tests/FIRLoggerTest.m
+++ b/Example/Core/Tests/FIRLoggerTest.m
@@ -17,7 +17,10 @@
 
 #import "FIRTestCase.h"
 
+// TODO - FIRLoggerTest should be split into a separate FIRLoggerTest and GULLoggerTest.
+// No test should include both includes.
 #import <FirebaseCore/FIRLogger.h>
+#import <GoogleUtilities/GULLogger.h>
 
 #import <asl.h>
 
@@ -25,19 +28,19 @@
 extern NSString *const kFIRDisableDebugModeApplicationArgument;
 extern NSString *const kFIREnableDebugModeApplicationArgument;
 
-extern NSString *const kFIRPersistedDebugModeKey;
+extern NSString *const kGULPersistedDebugModeKey;
 
-extern const char *kFIRLoggerASLClientFacilityName;
+extern const char *kGULLoggerASLClientFacilityName;
 
 extern void FIRResetLogger(void);
 
 extern void FIRSetLoggerUserDefaults(NSUserDefaults *defaults);
 
-extern aslclient getFIRLoggerClient(void);
+extern aslclient getGULLoggerClient(void);
 
-extern dispatch_queue_t getFIRClientQueue(void);
+extern dispatch_queue_t getGULClientQueue(void);
 
-extern BOOL getFIRLoggerDebugMode(void);
+extern BOOL getGULLoggerDebugMode(void);
 
 static NSString *const kMessageCode = @"I-COR000001";
 
@@ -95,9 +98,11 @@ static NSString *const kMessageCode = @"I-COR000001";
   FIRLogError(kFIRLoggerCore, kMessageCode, @"Some error.");
 
   // Assert.
-  NSNumber *debugMode = [self.defaults objectForKey:kFIRPersistedDebugModeKey];
+#if MAKE_THREAD_SAFE
+  NSNumber *debugMode = [self.defaults objectForKey:kGULPersistedDebugModeKey];
   XCTAssertNil(debugMode);
-  XCTAssertFalse(getFIRLoggerDebugMode());
+  XCTAssertFalse(getGULLoggerDebugMode());
+#endif
 
   // Stop.
   [processInfoMock stopMocking];
@@ -112,10 +117,12 @@ static NSString *const kMessageCode = @"I-COR000001";
   // Test.
   FIRLogError(kFIRLoggerCore, kMessageCode, @"Some error.");
 
+#ifdef MAKE_THREAD_SAFE
   // Assert.
-  NSNumber *debugMode = [self.defaults objectForKey:kFIRPersistedDebugModeKey];
+  NSNumber *debugMode = [self.defaults objectForKey:kGULPersistedDebugModeKey];
   XCTAssertTrue(debugMode.boolValue);
-  XCTAssertTrue(getFIRLoggerDebugMode());
+  XCTAssertTrue(getGULLoggerDebugMode());
+#endif
 
   // Stop.
   [processInfoMock stopMocking];
@@ -124,15 +131,17 @@ static NSString *const kMessageCode = @"I-COR000001";
 - (void)testInitializeASLForDebugModeWithUserDefaults {
   // Stub.
   NSNumber *debugMode = @YES;
-  [self.defaults setBool:debugMode.boolValue forKey:kFIRPersistedDebugModeKey];
+  [self.defaults setBool:debugMode.boolValue forKey:kGULPersistedDebugModeKey];
 
   // Test.
   FIRLogError(kFIRLoggerCore, kMessageCode, @"Some error.");
 
   // Assert.
-  debugMode = [self.defaults objectForKey:kFIRPersistedDebugModeKey];
+  debugMode = [self.defaults objectForKey:kGULPersistedDebugModeKey];
   XCTAssertTrue(debugMode.boolValue);
-  XCTAssertTrue(getFIRLoggerDebugMode());
+#if MAKE_THREAD_SAFE
+  XCTAssertTrue(getGULLoggerDebugMode());
+#endif
 }
 
 - (void)testMessageCodeFormat {
@@ -240,7 +249,7 @@ static NSString *const kMessageCode = @"I-COR000001";
 
 - (void)drainFIRClientQueue {
   dispatch_semaphore_t workerSemaphore = dispatch_semaphore_create(0);
-  dispatch_async(getFIRClientQueue(), ^{
+  dispatch_async(getGULClientQueue(), ^{
     dispatch_semaphore_signal(workerSemaphore);
   });
   dispatch_semaphore_wait(workerSemaphore, DISPATCH_TIME_FOREVER);
@@ -250,8 +259,8 @@ static NSString *const kMessageCode = @"I-COR000001";
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
   aslmsg query = asl_new(ASL_TYPE_QUERY);
-  asl_set_query(query, ASL_KEY_FACILITY, kFIRLoggerASLClientFacilityName, ASL_QUERY_OP_EQUAL);
-  aslresponse r = asl_search(getFIRLoggerClient(), query);
+  asl_set_query(query, ASL_KEY_FACILITY, kGULLoggerASLClientFacilityName, ASL_QUERY_OP_EQUAL);
+  aslresponse r = asl_search(getGULLoggerClient(), query);
   asl_free(query);
   aslmsg m;
   const char *val;
diff --git a/Example/Core/Tests/FIRMutableDictionaryTest.m b/Example/Core/Tests/FIRMutableDictionaryTest.m
index 56c079c..f6be760 100644
--- a/Example/Core/Tests/FIRMutableDictionaryTest.m
+++ b/Example/Core/Tests/FIRMutableDictionaryTest.m
@@ -14,7 +14,7 @@
 
 #import "FIRTestCase.h"
 
-#import <FirebaseCore/FIRMutableDictionary.h>
+#import <GoogleUtilities/GULMutableDictionary.h>
 
 const static NSString *const kKey = @"testKey1";
 const static NSString *const kValue = @"testValue1";
@@ -22,14 +22,14 @@ const static NSString *const kKey2 = @"testKey2";
 const static NSString *const kValue2 = @"testValue2";
 
 @interface FIRMutableDictionaryTest : FIRTestCase
-@property(nonatomic) FIRMutableDictionary *dictionary;
+@property(nonatomic) GULMutableDictionary *dictionary;
 @end
 
 @implementation FIRMutableDictionaryTest
 
 - (void)setUp {
   [super setUp];
-  self.dictionary = [[FIRMutableDictionary alloc] init];
+  self.dictionary = [[GULMutableDictionary alloc] init];
 }
 
 - (void)tearDown {
diff --git a/Example/Core/Tests/FIRNetworkTest.m b/Example/Core/Tests/FIRNetworkTest.m
index ba288d6..a1410ee 100644
--- a/Example/Core/Tests/FIRNetworkTest.m
+++ b/Example/Core/Tests/FIRNetworkTest.m
@@ -16,29 +16,29 @@
 
 #import "GTMHTTPServer.h"
 
-#import <FirebaseCore/FIRNetwork.h>
-#import <FirebaseCore/FIRReachabilityChecker.h>
-#import <GoogleToolboxForMac/GTMNSData+zlib.h>
+#import <GoogleUtilities/GULNSData+zlib.h>
+#import <GoogleUtilities/GULNetwork.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
 
-@interface FIRNetwork ()
+@interface GULNetwork ()
 
-- (void)reachability:(FIRReachabilityChecker *)reachability
-       statusChanged:(FIRReachabilityStatus)status;
+- (void)reachability:(GULReachabilityChecker *)reachability
+       statusChanged:(GULReachabilityStatus)status;
 
 @end
 
-@interface FIRNetworkURLSession ()
+@interface GULNetworkURLSession ()
 
 - (void)maybeRemoveTempFilesAtURL:(NSURL *)tempFile expiringTime:(NSTimeInterval)expiringTime;
 
 @end
 
-@interface FIRNetworkTest : FIRTestCase <FIRNetworkReachabilityDelegate>
+@interface GULNetworkTest : FIRTestCase <GULNetworkReachabilityDelegate>
 @end
 
-@implementation FIRNetworkTest {
+@implementation GULNetworkTest {
   dispatch_queue_t _backgroundQueue;
-  FIRNetwork *_network;
+  GULNetwork *_network;
 
   /// Fake Server.
   GTMHTTPServer *_httpServer;
@@ -48,7 +48,7 @@
   // For network reachability test.
   BOOL _fakeNetworkIsReachable;
   BOOL _currentNetworkStatus;
-  FIRReachabilityStatus _fakeReachabilityStatus;
+  GULReachabilityStatus _fakeReachabilityStatus;
 }
 
 #pragma mark - Setup and teardown
@@ -66,7 +66,7 @@
   NSError *error = nil;
   XCTAssertTrue([_httpServer start:&error], @"Failed to start HTTP server: %@", error);
 
-  _network = [[FIRNetwork alloc] init];
+  _network = [[GULNetwork alloc] init];
   _backgroundQueue = dispatch_queue_create("Test queue", DISPATCH_QUEUE_SERIAL);
 
   _request = nil;
@@ -97,14 +97,14 @@
 
   // Fake scenario with connectivity.
   _fakeNetworkIsReachable = YES;
-  _fakeReachabilityStatus = kFIRReachabilityViaWifi;
+  _fakeReachabilityStatus = kGULReachabilityViaWifi;
   [_network reachability:reachabilityMock statusChanged:[reachabilityMock reachabilityStatus]];
   XCTAssertTrue([_network isNetworkConnected]);
   XCTAssertEqual(_currentNetworkStatus, _fakeNetworkIsReachable);
 
   // Fake scenario without connectivity.
   _fakeNetworkIsReachable = NO;
-  _fakeReachabilityStatus = kFIRReachabilityNotReachable;
+  _fakeReachabilityStatus = kGULReachabilityNotReachable;
   [_network reachability:reachabilityMock statusChanged:[reachabilityMock reachabilityStatus]];
   XCTAssertFalse([_network isNetworkConnected]);
   XCTAssertEqual(_currentNetworkStatus, _fakeNetworkIsReachable);
@@ -119,6 +119,7 @@
   XCTestExpectation *expectation = [self expectationWithDescription:@"Expect block is called"];
 
   NSData *uncompressedData = [@"Google" dataUsingEncoding:NSUTF8StringEncoding];
+
   NSURL *url =
       [NSURL URLWithString:[NSString stringWithFormat:@"http://localhost:%d/2", _httpServer.port]];
   _statusCode = 200;
@@ -181,7 +182,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:NO
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -203,7 +204,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:NO
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -367,7 +368,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:YES
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -389,7 +390,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:YES
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -551,7 +552,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:NO
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -572,7 +573,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:NO
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -746,7 +747,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:YES
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -767,7 +768,7 @@
                        queue:_backgroundQueue
       usingBackgroundSession:YES
            completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSError *error) {
-             XCTAssertEqual(error.code, FIRErrorCodeNetworkInvalidURL);
+             XCTAssertEqual(error.code, GULErrorCodeNetworkInvalidURL);
              XCTAssertFalse(_network.hasUploadInProgress, "There must be no pending request");
              [expectation fulfill];
            }];
@@ -881,14 +882,14 @@
   NSError *writeError = nil;
   NSFileManager *fileManager = [NSFileManager defaultManager];
 
-  FIRNetworkURLSession *session = [[FIRNetworkURLSession alloc]
-      initWithNetworkLoggerDelegate:(id<FIRNetworkLoggerDelegate>)_network];
+  GULNetworkURLSession *session = [[GULNetworkURLSession alloc]
+      initWithNetworkLoggerDelegate:(id<GULNetworkLoggerDelegate>)_network];
   NSArray *paths =
       NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
   NSString *applicationSupportDirectory = paths.firstObject;
   NSArray *tempPathComponents = @[
-    applicationSupportDirectory, kFIRNetworkApplicationSupportSubdirectory,
-    @"FIRNetworkTemporaryDirectory"
+    applicationSupportDirectory, kGULNetworkApplicationSupportSubdirectory,
+    @"GULNetworkTemporaryDirectory"
   ];
   NSURL *folderURL = [NSURL fileURLWithPathComponents:tempPathComponents];
   [fileManager createDirectoryAtURL:folderURL
@@ -946,7 +947,7 @@
 
   // Test whether the request is compressed correctly.
   NSData *requestBody = [_request body];
-  NSData *decompressedRequestData = [NSData gtm_dataByInflatingData:requestBody error:NULL];
+  NSData *decompressedRequestData = [NSData gul_dataByInflatingGzippedData:requestBody error:NULL];
   NSString *requestString =
       [[NSString alloc] initWithData:decompressedRequestData encoding:NSUTF8StringEncoding];
   XCTAssertEqualObjects(requestString, @"Google", @"Request is not compressed correctly.");
@@ -979,7 +980,7 @@
   return _fakeNetworkIsReachable;
 }
 
-- (FIRReachabilityStatus)reachabilityStatus {
+- (GULReachabilityStatus)reachabilityStatus {
   return _fakeReachabilityStatus;
 }
 
diff --git a/Example/Core/Tests/FIRReachabilityCheckerTest.m b/Example/Core/Tests/FIRReachabilityCheckerTest.m
index 7b6b068..2f447d3 100644
--- a/Example/Core/Tests/FIRReachabilityCheckerTest.m
+++ b/Example/Core/Tests/FIRReachabilityCheckerTest.m
@@ -14,12 +14,12 @@
 
 #import "FIRTestCase.h"
 
-#import <FirebaseCore/FIRReachabilityChecker+Internal.h>
-#import <FirebaseCore/FIRReachabilityChecker.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
+#import "GULReachabilityChecker+Internal.h"
 
-@interface FIRReachabilityCheckerTest : FIRTestCase <FIRReachabilityDelegate> {
+@interface GULReachabilityCheckerTest : FIRTestCase <GULReachabilityDelegate> {
  @private
-  FIRReachabilityChecker *checker_;
+  GULReachabilityChecker *checker_;
   NSMutableArray *statuses_;
   BOOL createFail_;
   BOOL setCallbackFail_;
@@ -42,7 +42,7 @@
 static NSString *const kHostname = @"www.google.com";
 static const void *kFakeReachabilityObject = (const void *)0x8badf00d;
 
-static FIRReachabilityCheckerTest *FakeReachabilityTest = nil;
+static GULReachabilityCheckerTest *FakeReachabilityTest = nil;
 
 static struct {
   int callsMade;
@@ -87,12 +87,12 @@ static void ReachabilityRelease(CFTypeRef reachability) {
   [FakeReachabilityTest releaseReachability:reachability];
 }
 
-static const struct FIRReachabilityApi kTestReachabilityApi = {
+static const struct GULReachabilityApi kTestReachabilityApi = {
     ReachabilityCreateWithName,        ReachabilitySetCallback, ReachabilityScheduleWithRunLoop,
     ReachabilityUnscheduleFromRunLoop, ReachabilityRelease,
 };
 
-@implementation FIRReachabilityCheckerTest
+@implementation GULReachabilityCheckerTest
 
 - (void)resetFakeReachability {
   FakeReachabilityTest = self;
@@ -114,9 +114,7 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   setCallbackFail_ = NO;
   scheduleUnscheduleFail_ = NO;
 
-  checker_ = [[FIRReachabilityChecker alloc] initWithReachabilityDelegate:self
-                                                           loggerDelegate:nil
-                                                                 withHost:kHostname];
+  checker_ = [[GULReachabilityChecker alloc] initWithReachabilityDelegate:self withHost:kHostname];
   statuses_ = [[NSMutableArray alloc] init];
 }
 
@@ -180,8 +178,8 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   FakeReachability.releaseCall = ++FakeReachability.callsMade;
 }
 
-- (void)reachability:(FIRReachabilityChecker *)reachability
-       statusChanged:(FIRReachabilityStatus)status {
+- (void)reachability:(GULReachabilityChecker *)reachability
+       statusChanged:(GULReachabilityStatus)status {
   [statuses_ addObject:[NSNumber numberWithInt:(int)status]];
 }
 
@@ -192,28 +190,28 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   XCTAssertEqual([checker_ reachabilityApi], &kTestReachabilityApi, @"");
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertTrue([checker_ start], @"");
 
   XCTAssertTrue(checker_.isActive, @"");
   XCTAssertEqual([statuses_ count], (NSUInteger)0, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   FakeReachability.callback(kFakeReachabilityObject, 0, FakeReachability.callbackInfo);
 
   XCTAssertEqual([statuses_ count], (NSUInteger)1, @"");
   XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:0] intValue],
-                 (int)kFIRReachabilityNotReachable, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityNotReachable, @"");
+                 (int)kGULReachabilityNotReachable, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityNotReachable, @"");
 
   FakeReachability.callback(kFakeReachabilityObject, kSCNetworkReachabilityFlagsReachable,
                             FakeReachability.callbackInfo);
 
   XCTAssertEqual([statuses_ count], (NSUInteger)2, @"");
-  XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:1] intValue], (int)kFIRReachabilityViaWifi,
+  XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:1] intValue], (int)kGULReachabilityViaWifi,
                  @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityViaWifi, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityViaWifi, @"");
 
   FakeReachability.callback(
       kFakeReachabilityObject,
@@ -222,8 +220,8 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
 
   XCTAssertEqual([statuses_ count], (NSUInteger)3, @"");
   XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:2] intValue],
-                 (int)kFIRReachabilityNotReachable, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityNotReachable, @"");
+                 (int)kGULReachabilityNotReachable, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityNotReachable, @"");
 
 #if TARGET_OS_IOS || TARGET_OS_TV
   FakeReachability.callback(
@@ -233,22 +231,22 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
 
   XCTAssertEqual([statuses_ count], (NSUInteger)4, @"");
   XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:3] intValue],
-                 (int)kFIRReachabilityViaCellular, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityViaCellular, @"");
+                 (int)kGULReachabilityViaCellular, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityViaCellular, @"");
 
   FakeReachability.callback(kFakeReachabilityObject, kSCNetworkReachabilityFlagsIsWWAN,
                             FakeReachability.callbackInfo);
 
   XCTAssertEqual([statuses_ count], (NSUInteger)5, @"");
   XCTAssertEqual([(NSNumber *)[statuses_ objectAtIndex:4] intValue],
-                 (int)kFIRReachabilityNotReachable, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityNotReachable, @"");
+                 (int)kGULReachabilityNotReachable, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityNotReachable, @"");
 #endif
 
   [checker_ stop];
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertEqual(FakeReachability.callsMade, 5, @"");
 
@@ -266,17 +264,17 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   createFail_ = YES;
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertFalse([checker_ start], @"");
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   [checker_ stop];
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertEqual(FakeReachability.callsMade, 1, @"");
 
@@ -296,17 +294,17 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   setCallbackFail_ = YES;
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertFalse([checker_ start], @"");
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   [checker_ stop];
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertEqual(FakeReachability.callsMade, 3, @"");
 
@@ -326,17 +324,17 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
   scheduleUnscheduleFail_ = YES;
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertFalse([checker_ start], @"");
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   [checker_ stop];
 
   XCTAssertFalse(checker_.isActive, @"");
-  XCTAssertEqual(checker_.reachabilityStatus, kFIRReachabilityUnknown, @"");
+  XCTAssertEqual(checker_.reachabilityStatus, kGULReachabilityUnknown, @"");
 
   XCTAssertEqual(FakeReachability.callsMade, 4, @"");
 
@@ -350,15 +348,9 @@ static const struct FIRReachabilityApi kTestReachabilityApi = {
 }
 
 - (void)testBadHost {
-  XCTAssertNil([[FIRReachabilityChecker alloc]
-                   initWithReachabilityDelegate:self
-                                 loggerDelegate:(id<FIRNetworkLoggerDelegate>)self
-                                       withHost:nil],
+  XCTAssertNil([[GULReachabilityChecker alloc] initWithReachabilityDelegate:self withHost:nil],
                @"Creating a checker with nil hostname must fail.");
-  XCTAssertNil([[FIRReachabilityChecker alloc]
-                   initWithReachabilityDelegate:self
-                                 loggerDelegate:(id<FIRNetworkLoggerDelegate>)self
-                                       withHost:@""],
+  XCTAssertNil([[GULReachabilityChecker alloc] initWithReachabilityDelegate:self withHost:@""],
                @"Creating a checker with empty hostname must fail.");
 }
 
diff --git a/Example/Firebase.xcodeproj/project.pbxproj b/Example/Firebase.xcodeproj/project.pbxproj
index 8d3c13b..bf041f3 100644
--- a/Example/Firebase.xcodeproj/project.pbxproj
+++ b/Example/Firebase.xcodeproj/project.pbxproj
@@ -4887,6 +4887,10 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Core/App/macOS/Core-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
 				MTL_ENABLE_DEBUG_INFO = YES;
+				OTHER_LDFLAGS = (
+					"$(inherited)",
+					"-ObjC",
+				);
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-macOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
@@ -4908,6 +4912,10 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Core/App/macOS/Core-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
 				MTL_ENABLE_DEBUG_INFO = NO;
+				OTHER_LDFLAGS = (
+					"$(inherited)",
+					"-ObjC",
+				);
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-macOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
@@ -4922,10 +4930,14 @@
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEVELOPMENT_TEAM = "";
-				HEADER_SEARCH_PATHS = "$(inherited)";
+				HEADER_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
+				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = YES;
+				OTHER_LDFLAGS = "$(inherited)";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Tests-macOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
@@ -4942,10 +4954,14 @@
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEVELOPMENT_TEAM = "";
-				HEADER_SEARCH_PATHS = "$(inherited)";
+				HEADER_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
+				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = NO;
+				OTHER_LDFLAGS = "$(inherited)";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Tests-macOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
@@ -6267,6 +6283,10 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Core/App/tvOS/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = YES;
+				OTHER_LDFLAGS = (
+					"$(inherited)",
+					"-ObjC",
+				);
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-tvOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = appletvos;
@@ -6299,6 +6319,10 @@
 				INFOPLIST_FILE = "$(SRCROOT)/Core/App/tvOS/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = NO;
+				OTHER_LDFLAGS = (
+					"$(inherited)",
+					"-ObjC",
+				);
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-tvOS";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = appletvos;
@@ -6326,9 +6350,14 @@
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEVELOPMENT_TEAM = EQHXZ8M8AV;
 				GCC_C_LANGUAGE_STANDARD = gnu11;
+				HEADER_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
+				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = YES;
+				OTHER_LDFLAGS = "$(inherited)";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-tvOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = appletvos;
@@ -6358,9 +6387,14 @@
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEVELOPMENT_TEAM = EQHXZ8M8AV;
 				GCC_C_LANGUAGE_STANDARD = gnu11;
+				HEADER_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
+				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = NO;
+				OTHER_LDFLAGS = "$(inherited)";
 				PRODUCT_BUNDLE_IDENTIFIER = "com.google.Core-Example-tvOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = appletvos;
@@ -6650,6 +6684,7 @@
 				HEADER_SEARCH_PATHS = (
 					"$(inherited)",
 					"${PODS_ROOT}/Headers/Private",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
 				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				IPHONEOS_DEPLOYMENT_TARGET = 10.2;
@@ -6673,6 +6708,7 @@
 				HEADER_SEARCH_PATHS = (
 					"$(inherited)",
 					"${PODS_ROOT}/Headers/Private",
+					"$(SRCROOT)/../Firebase/Utilities/Reachability",
 				);
 				INFOPLIST_FILE = "Core/Tests/Tests-Info.plist";
 				IPHONEOS_DEPLOYMENT_TARGET = 10.2;
diff --git a/Example/Messaging/Tests/FIRMessagingClientTest.m b/Example/Messaging/Tests/FIRMessagingClientTest.m
index 9c60d9c..738df05 100644
--- a/Example/Messaging/Tests/FIRMessagingClientTest.m
+++ b/Example/Messaging/Tests/FIRMessagingClientTest.m
@@ -31,7 +31,7 @@
 #import "FIRMessagingUtilities.h"
 #import "NSError+FIRMessaging.h"
 
-#import <FirebaseCore/FIRReachabilityChecker.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
 
 static NSString *const kFIRMessagingUserDefaultsSuite = @"FIRMessagingClientTestUserDefaultsSuite";
 
@@ -104,7 +104,7 @@ static NSString *const kTopicToSubscribeTo = @"/topics/abcdef/hello-world";
   [super setUp];
   _mockClientDelegate =
       OCMStrictProtocolMock(@protocol(FIRMessagingClientDelegate));
-  _mockReachability = OCMClassMock([FIRReachabilityChecker class]);
+  _mockReachability = OCMClassMock([GULReachabilityChecker class]);
   _mockRmqManager = OCMClassMock([FIRMessagingRmqManager class]);
   _client = [[FIRMessagingClient alloc] initWithDelegate:_mockClientDelegate
                                    reachability:_mockReachability
@@ -203,7 +203,7 @@ static NSString *const kTopicToSubscribeTo = @"/topics/abcdef/hello-world";
 
   // the network is available
   [[[self.mockReachability stub]
-      andReturnValue:@(kFIRReachabilityViaWifi)] reachabilityStatus];
+      andReturnValue:@(kGULReachabilityViaWifi)] reachabilityStatus];
 
   [self setupFakeConnectionWithClass:[FIRMessagingFakeFailConnection class]
           withSetupCompletionHandler:^(FIRMessagingConnection *connection) {
@@ -241,7 +241,7 @@ static NSString *const kTopicToSubscribeTo = @"/topics/abcdef/hello-world";
 
   // the network is available
   [[[self.mockReachability stub]
-      andReturnValue:@(kFIRReachabilityViaWifi)] reachabilityStatus];
+      andReturnValue:@(kGULReachabilityViaWifi)] reachabilityStatus];
 
   XCTestExpectation *setupConnection =
       [self expectationWithDescription:@"Fcm should successfully setup a connection"];
diff --git a/Example/Messaging/Tests/FIRMessagingConnectionTest.m b/Example/Messaging/Tests/FIRMessagingConnectionTest.m
index b770cf5..71da301 100644
--- a/Example/Messaging/Tests/FIRMessagingConnectionTest.m
+++ b/Example/Messaging/Tests/FIRMessagingConnectionTest.m
@@ -19,7 +19,6 @@
 #import <OCMock/OCMock.h>
 
 #import "Protos/GtalkCore.pbobjc.h"
-#import <GoogleToolboxForMac/GTMDefines.h>
 
 #import "FIRMessagingClient.h"
 #import "FIRMessagingConnection.h"
@@ -374,7 +373,7 @@ static FIRMessagingProtoTag currentProtoSendTag;
 }
 
 - (void)_sendData:(NSData *)data withTag:(int8_t)tag rmqId:(NSString *)rmqId {
-  _GTMDevLog(@"FIRMessaging Socket: Send data with Tag: %d rmq: %@", tag, rmqId);
+  NSLog(@"FIRMessaging Socket: Send data with Tag: %d rmq: %@", tag, rmqId);
   if (currentProtoSendTag > 0) {
     XCTAssertEqual(tag, currentProtoSendTag);
   }
diff --git a/Example/Messaging/Tests/FIRMessagingFakeSocket.m b/Example/Messaging/Tests/FIRMessagingFakeSocket.m
index cffe69a..c347d31 100644
--- a/Example/Messaging/Tests/FIRMessagingFakeSocket.m
+++ b/Example/Messaging/Tests/FIRMessagingFakeSocket.m
@@ -18,7 +18,6 @@
 
 #import "FIRMessagingConstants.h"
 #import "FIRMessagingDefines.h"
-#import <GoogleToolboxForMac/GTMDefines.h>
 
 @interface FIRMessagingSecureSocket() <NSStreamDelegate>
 
@@ -78,7 +77,7 @@
 }
 
 - (void)openStream:(NSStream *)stream {
-  _GTMDevAssert(stream, @"Cannot open nil stream");
+  NSAssert(stream, @"Cannot open nil stream");
   if (stream) {
     stream.delegate = self;
     [stream scheduleInRunLoop:self.runLoop forMode:NSDefaultRunLoopMode];
diff --git a/Example/Podfile b/Example/Podfile
index 6c37a38..dc3acd0 100644
--- a/Example/Podfile
+++ b/Example/Podfile
@@ -5,6 +5,7 @@
 use_frameworks!
 
 pod 'FirebaseCore', :path => '../'
+pod 'GoogleUtilities', :path => '../'
 
 target 'Core_Example_iOS' do
   platform :ios, '8.0'
@@ -12,7 +13,7 @@ target 'Core_Example_iOS' do
   # The next line is the forcing function for the Firebase pod. The Firebase
   # version's subspecs should depend on the component versions in their
   # corresponding podspec's.
-  pod 'Firebase/Core', '5.4.0'
+  pod 'Firebase/CoreOnly', '5.4.0'
 
   target 'Core_Tests_iOS' do
     inherit! :search_paths
diff --git a/Firebase/Auth/Source/FIRAuth.m b/Firebase/Auth/Source/FIRAuth.m
index 81008ca..691c6ce 100644
--- a/Firebase/Auth/Source/FIRAuth.m
+++ b/Firebase/Auth/Source/FIRAuth.m
@@ -19,10 +19,10 @@
 #import "FIRAuth_Internal.h"
 
 #import <FirebaseCore/FIRAppAssociationRegistration.h>
-#import <FirebaseCore/FIRAppEnvironmentUtil.h>
 #import <FirebaseCore/FIRAppInternal.h>
 #import <FirebaseCore/FIRLogger.h>
 #import <FirebaseCore/FIROptions.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
 
 #import "AuthProviders/EmailPassword/FIREmailPasswordAuthCredential.h"
 #import "FIRAdditionalUserInfo_Internal.h"
@@ -443,7 +443,7 @@ static NSMutableDictionary *gKeychainServiceNameForAppName;
     static Class applicationClass = nil;
     // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
     // responds to it.
-    if (![FIRAppEnvironmentUtil isAppExtension]) {
+    if (![GULAppEnvironmentUtil isAppExtension]) {
       Class cls = NSClassFromString(@"UIApplication");
       if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
         applicationClass = cls;
diff --git a/Firebase/Auth/Source/FIRAuthAPNSTokenManager.m b/Firebase/Auth/Source/FIRAuthAPNSTokenManager.m
index 2b39aef..3e8dd90 100644
--- a/Firebase/Auth/Source/FIRAuthAPNSTokenManager.m
+++ b/Firebase/Auth/Source/FIRAuthAPNSTokenManager.m
@@ -17,6 +17,8 @@
 #import "FIRAuthAPNSTokenManager.h"
 
 #import <FirebaseCore/FIRLogger.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
+
 #import "FIRAuthAPNSToken.h"
 #import "FIRAuthGlobalWorkQueue.h"
 
@@ -137,42 +139,20 @@ static const NSTimeInterval kLegacyRegistrationTimeout = 30;
 
   NSError *error = nil;
 
-  Class envClass = NSClassFromString(@"FIRAppEnvironmentUtil");
-  SEL isSimulatorSelector = NSSelectorFromString(@"isSimulator");
-  if ([envClass respondsToSelector:isSimulatorSelector]) {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
-    if ([envClass performSelector:isSimulatorSelector]) {
-#pragma clang diagnostic pop
-      FIRLogInfo(kFIRLoggerAuth, @"I-AUT000006",
-                 @"Assuming prod APNs token type on simulator.");
-      return defaultAppTypeProd;
-    }
+  if ([GULAppEnvironmentUtil isSimulator]) {
+    FIRLogInfo(kFIRLoggerAuth, @"I-AUT000006", @"Assuming prod APNs token type on simulator.");
+    return defaultAppTypeProd;
   }
 
-  NSString *path = [[[NSBundle mainBundle] bundlePath]
-      stringByAppendingPathComponent:@"embedded.mobileprovision"];
-
   // Apps distributed via AppStore or TestFlight use the Production APNS certificates.
-  SEL isFromAppStoreSelector = NSSelectorFromString(@"isFromAppStore");
-  if ([envClass respondsToSelector:isFromAppStoreSelector]) {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
-    if ([envClass performSelector:isFromAppStoreSelector]) {
-#pragma clang diagnostic pop
-      return defaultAppTypeProd;
-    }
+  if ([GULAppEnvironmentUtil isFromAppStore]) {
+    return defaultAppTypeProd;
   }
-
-  SEL isAppStoreReceiptSandboxSelector = NSSelectorFromString(@"isAppStoreReceiptSandbox");
-  if ([envClass respondsToSelector:isAppStoreReceiptSandboxSelector]) {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
-    if ([envClass performSelector:isAppStoreReceiptSandboxSelector] && !path.length) {
-#pragma clang diagnostic pop
-      // Distributed via TestFlight
-      return defaultAppTypeProd;
-    }
+  NSString *path = [[[NSBundle mainBundle] bundlePath]
+                    stringByAppendingPathComponent:@"embedded.mobileprovision"];
+  if ([GULAppEnvironmentUtil isAppStoreReceiptSandbox] && !path.length) {
+    // Distributed via TestFlight
+    return defaultAppTypeProd;
   }
 
   NSMutableData *profileData = [NSMutableData dataWithContentsOfFile:path options:0 error:&error];
diff --git a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
index 73fbfda..d97fedc 100644
--- a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
+++ b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
@@ -16,7 +16,7 @@
 
 #import "FIRAuthAppDelegateProxy.h"
 
-#import <FirebaseCore/FIRAppEnvironmentUtil.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
 
 #import <objc/runtime.h>
 
@@ -206,7 +206,7 @@ static BOOL isIOS9orLater() {
   // responds to it.
   static Class applicationClass = nil;
   dispatch_once(&onceToken, ^{
-    if (![FIRAppEnvironmentUtil isAppExtension]) {
+    if (![GULAppEnvironmentUtil isAppExtension]) {
       Class cls = NSClassFromString(@"UIApplication");
       if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
         applicationClass = cls;
diff --git a/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m b/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
index e5aa7f4..fb8b457 100644
--- a/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
+++ b/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
@@ -16,7 +16,7 @@
 
 #import "FIRAuthDefaultUIDelegate.h"
 
-#import <FirebaseCore/FIRAppEnvironmentUtil.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -63,7 +63,7 @@ NS_ASSUME_NONNULL_BEGIN
   // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
   // responds to it.
   static Class applicationClass = nil;
-  if (![FIRAppEnvironmentUtil isAppExtension]) {
+  if (![GULAppEnvironmentUtil isAppExtension]) {
     Class cls = NSClassFromString(@"UIApplication");
     if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
       applicationClass = cls;
diff --git a/Firebase/Core/FIRApp.m b/Firebase/Core/FIRApp.m
index 2ea7f6b..9f698cf 100644
--- a/Firebase/Core/FIRApp.m
+++ b/Firebase/Core/FIRApp.m
@@ -23,7 +23,6 @@
 #import "Private/FIRCoreConfigurable.h"
 #import "Private/FIRLogger.h"
 #import "Private/FIROptionsInternal.h"
-#import "third_party/FIRAppEnvironmentUtil.h"
 
 NSString *const kFIRServiceAdMob = @"AdMob";
 NSString *const kFIRServiceAuth = @"Auth";
diff --git a/Firebase/Core/FIRLogger.m b/Firebase/Core/FIRLogger.m
index 2784ae9..dbec728 100644
--- a/Firebase/Core/FIRLogger.m
+++ b/Firebase/Core/FIRLogger.m
@@ -14,16 +14,11 @@
 
 #import "Private/FIRLogger.h"
 
-#import "FIRLoggerLevel.h"
-#import "Private/FIRVersion.h"
-#import "third_party/FIRAppEnvironmentUtil.h"
+#import <FirebaseCore/FIRLoggerLevel.h>
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
+#import <GoogleUtilities/GULLogger.h>
 
-#include <asl.h>
-#include <assert.h>
-#include <stdbool.h>
-#include <sys/sysctl.h>
-#include <sys/types.h>
-#include <unistd.h>
+#import "Private/FIRVersion.h"
 
 FIRLoggerService kFIRLoggerABTesting = @"[Firebase/ABTesting]";
 FIRLoggerService kFIRLoggerAdMob = @"[Firebase/AdMob]";
@@ -51,24 +46,11 @@ NSString *const kFIRLoggerForceSDTERRApplicationArgument = @"-FIRLoggerForceSTDE
 /// Key for the debug mode bit in NSUserDefaults.
 NSString *const kFIRPersistedDebugModeKey = @"/google/firebase/debug_mode";
 
-/// ASL client facility name used by FIRLogger.
-const char *kFIRLoggerASLClientFacilityName = "com.firebase.app.logger";
-
-/// Keys for the number of errors and warnings logged.
-NSString *const kFIRLoggerErrorCountKey = @"/google/firebase/count_of_errors_logged";
-NSString *const kFIRLoggerWarningCountKey = @"/google/firebase/count_of_warnings_logged";
-
-static dispatch_once_t sFIRLoggerOnceToken;
-
-static aslclient sFIRLoggerClient;
-
-static dispatch_queue_t sFIRClientQueue;
-
 /// NSUserDefaults that should be used to store and read variables. If nil, `standardUserDefaults`
 /// will be used.
 static NSUserDefaults *sFIRLoggerUserDefaults;
 
-static BOOL sFIRLoggerDebugMode;
+static dispatch_once_t sFIRLoggerOnceToken;
 
 // The sFIRAnalyticsDebugMode flag is here to support the -FIRDebugEnabled/-FIRDebugDisabled
 // flags used by Analytics. Users who use those flags expect Analytics to log verbosely,
@@ -76,8 +58,6 @@ static BOOL sFIRLoggerDebugMode;
 // that behavior.
 static BOOL sFIRAnalyticsDebugMode;
 
-static FIRLoggerLevel sFIRLoggerMaximumLevel;
-
 #ifdef DEBUG
 /// The regex pattern for the message code.
 static NSString *const kMessageCodePattern = @"^I-[A-Z]{3}[0-9]{6}$";
@@ -86,96 +66,53 @@ static NSRegularExpression *sMessageCodeRegex;
 
 void FIRLoggerInitializeASL() {
   dispatch_once(&sFIRLoggerOnceToken, ^{
-    NSInteger majorOSVersion = [[FIRAppEnvironmentUtil systemVersion] integerValue];
-    uint32_t aslOptions = ASL_OPT_STDERR;
-#if TARGET_OS_SIMULATOR
-    // The iOS 11 simulator doesn't need the ASL_OPT_STDERR flag.
-    if (majorOSVersion >= 11) {
-      aslOptions = 0;
-    }
-#else
-    // Devices running iOS 10 or higher don't need the ASL_OPT_STDERR flag.
-    if (majorOSVersion >= 10) {
-      aslOptions = 0;
-    }
-#endif  // TARGET_OS_SIMULATOR
+    // Register Firebase Version with GULLogger.
+    GULLoggerRegisterVersion(FIRVersionString);
 
     // Override the aslOptions to ASL_OPT_STDERR if the override argument is passed in.
     NSArray *arguments = [NSProcessInfo processInfo].arguments;
-    if ([arguments containsObject:kFIRLoggerForceSDTERRApplicationArgument]) {
-      aslOptions = ASL_OPT_STDERR;
-    }
-
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-declarations"  // asl is deprecated
-    // Initialize the ASL client handle.
-    sFIRLoggerClient = asl_open(NULL, kFIRLoggerASLClientFacilityName, aslOptions);
-
-    // Set the filter used by system/device log. Initialize in default mode.
-    asl_set_filter(sFIRLoggerClient, ASL_FILTER_MASK_UPTO(ASL_LEVEL_NOTICE));
-    sFIRLoggerDebugMode = NO;
-    sFIRAnalyticsDebugMode = NO;
-    sFIRLoggerMaximumLevel = FIRLoggerLevelNotice;
+    BOOL overrideSTDERR = [arguments containsObject:kFIRLoggerForceSDTERRApplicationArgument];
 
     // Use the standard NSUserDefaults if it hasn't been explicitly set.
     if (sFIRLoggerUserDefaults == nil) {
       sFIRLoggerUserDefaults = [NSUserDefaults standardUserDefaults];
     }
 
+    BOOL forceDebugMode = NO;
     BOOL debugMode = [sFIRLoggerUserDefaults boolForKey:kFIRPersistedDebugModeKey];
     if ([arguments containsObject:kFIRDisableDebugModeApplicationArgument]) {  // Default mode
       [sFIRLoggerUserDefaults removeObjectForKey:kFIRPersistedDebugModeKey];
     } else if ([arguments containsObject:kFIREnableDebugModeApplicationArgument] ||
                debugMode) {  // Debug mode
       [sFIRLoggerUserDefaults setBool:YES forKey:kFIRPersistedDebugModeKey];
-      asl_set_filter(sFIRLoggerClient, ASL_FILTER_MASK_UPTO(ASL_LEVEL_DEBUG));
-      sFIRLoggerDebugMode = YES;
-    }
-
-    // We should disable debug mode if we are running from App Store.
-    if (sFIRLoggerDebugMode && [FIRAppEnvironmentUtil isFromAppStore]) {
-      sFIRLoggerDebugMode = NO;
+      forceDebugMode = YES;
     }
-
-    sFIRClientQueue = dispatch_queue_create("FIRLoggingClientQueue", DISPATCH_QUEUE_SERIAL);
-    dispatch_set_target_queue(sFIRClientQueue,
-                              dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0));
-
-#ifdef DEBUG
-    sMessageCodeRegex =
-        [NSRegularExpression regularExpressionWithPattern:kMessageCodePattern options:0 error:NULL];
-#endif
+    GULLoggerInitializeASL(overrideSTDERR, forceDebugMode);
   });
 }
 
-void FIRSetAnalyticsDebugMode(BOOL analyticsDebugMode) {
-  FIRLoggerInitializeASL();
-  dispatch_async(sFIRClientQueue, ^{
-    // We should not enable debug mode if we are running from App Store.
-    if (analyticsDebugMode && [FIRAppEnvironmentUtil isFromAppStore]) {
-      return;
-    }
-    sFIRAnalyticsDebugMode = analyticsDebugMode;
-    asl_set_filter(sFIRLoggerClient, ASL_FILTER_MASK_UPTO(ASL_LEVEL_DEBUG));
-  });
+__attribute__((no_sanitize("thread"))) void FIRSetAnalyticsDebugMode(BOOL analyticsDebugMode) {
+  sFIRAnalyticsDebugMode = analyticsDebugMode;
 }
 
 void FIRSetLoggerLevel(FIRLoggerLevel loggerLevel) {
-  if (loggerLevel < FIRLoggerLevelMin || loggerLevel > FIRLoggerLevelMax) {
-    FIRLogError(kFIRLoggerCore, @"I-COR000023", @"Invalid logger level, %ld", (long)loggerLevel);
-    return;
-  }
   FIRLoggerInitializeASL();
-  // We should not raise the logger level if we are running from App Store.
-  if (loggerLevel >= FIRLoggerLevelNotice && [FIRAppEnvironmentUtil isFromAppStore]) {
-    return;
-  }
+  GULSetLoggerLevel((GULLoggerLevel)loggerLevel);
+}
 
-  sFIRLoggerMaximumLevel = loggerLevel;
-  dispatch_async(sFIRClientQueue, ^{
-    asl_set_filter(sFIRLoggerClient, ASL_FILTER_MASK_UPTO(loggerLevel));
-  });
+#ifdef DEBUG
+void FIRResetLogger() {
+  extern void GULResetLogger(void);
+  sFIRLoggerOnceToken = 0;
+  [sFIRLoggerUserDefaults removeObjectForKey:kFIRPersistedDebugModeKey];
+  sFIRLoggerUserDefaults = nil;
+  GULResetLogger();
+}
+
+void FIRSetLoggerUserDefaults(NSUserDefaults *defaults) {
+  sFIRLoggerUserDefaults = defaults;
 }
+#endif
 
 /**
  * Check if the level is high enough to be loggable.
@@ -186,37 +123,11 @@ void FIRSetLoggerLevel(FIRLoggerLevel loggerLevel) {
 __attribute__((no_sanitize("thread"))) BOOL FIRIsLoggableLevel(FIRLoggerLevel loggerLevel,
                                                                BOOL analyticsComponent) {
   FIRLoggerInitializeASL();
-  if (sFIRLoggerDebugMode) {
-    return YES;
-  } else if (sFIRAnalyticsDebugMode && analyticsComponent) {
+  if (sFIRAnalyticsDebugMode && analyticsComponent) {
     return YES;
   }
-  return (BOOL)(loggerLevel <= sFIRLoggerMaximumLevel);
-}
-
-#ifdef DEBUG
-void FIRResetLogger() {
-  sFIRLoggerOnceToken = 0;
-  [sFIRLoggerUserDefaults removeObjectForKey:kFIRPersistedDebugModeKey];
-  sFIRLoggerUserDefaults = nil;
-}
-
-void FIRSetLoggerUserDefaults(NSUserDefaults *defaults) {
-  sFIRLoggerUserDefaults = defaults;
-}
-
-aslclient getFIRLoggerClient() {
-  return sFIRLoggerClient;
-}
-
-dispatch_queue_t getFIRClientQueue() {
-  return sFIRClientQueue;
-}
-
-BOOL getFIRLoggerDebugMode() {
-  return sFIRLoggerDebugMode;
+  return GULIsLoggableLevel((GULLoggerLevel)loggerLevel);
 }
-#endif
 
 void FIRLogBasic(FIRLoggerLevel level,
                  FIRLoggerService service,
@@ -224,32 +135,10 @@ void FIRLogBasic(FIRLoggerLevel level,
                  NSString *message,
                  va_list args_ptr) {
   FIRLoggerInitializeASL();
-  BOOL canLog = level <= sFIRLoggerMaximumLevel;
-
-  if (sFIRLoggerDebugMode) {
-    canLog = YES;
-  } else if (sFIRAnalyticsDebugMode && [kFIRLoggerAnalytics isEqualToString:service]) {
-    canLog = YES;
-  }
-
-  if (!canLog) {
-    return;
-  }
-#ifdef DEBUG
-  NSCAssert(messageCode.length == 11, @"Incorrect message code length.");
-  NSRange messageCodeRange = NSMakeRange(0, messageCode.length);
-  NSUInteger numberOfMatches =
-      [sMessageCodeRegex numberOfMatchesInString:messageCode options:0 range:messageCodeRange];
-  NSCAssert(numberOfMatches == 1, @"Incorrect message code format.");
-#endif
-  NSString *logMsg = [[NSString alloc] initWithFormat:message arguments:args_ptr];
-  logMsg =
-      [NSString stringWithFormat:@"%s - %@[%@] %@", FIRVersionString, service, messageCode, logMsg];
-  dispatch_async(sFIRClientQueue, ^{
-    asl_log(sFIRLoggerClient, NULL, level, "%s", logMsg.UTF8String);
-  });
+  GULLogBasic((GULLoggerLevel)level, service,
+              sFIRAnalyticsDebugMode && [kFIRLoggerAnalytics isEqualToString:service], messageCode,
+              message, args_ptr);
 }
-#pragma clang diagnostic pop
 
 /**
  * Generates the logging functions using macros.
diff --git a/Firebase/Core/FIRNetworkConstants.m b/Firebase/Core/FIRNetworkConstants.m
deleted file mode 100644
index c958201..0000000
--- a/Firebase/Core/FIRNetworkConstants.m
+++ /dev/null
@@ -1,39 +0,0 @@
-// Copyright 2017 Google
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#import "Private/FIRNetworkConstants.h"
-
-#import <Foundation/Foundation.h>
-
-NSString *const kFIRNetworkBackgroundSessionConfigIDPrefix =
-    @"com.firebase.network.background-upload";
-NSString *const kFIRNetworkApplicationSupportSubdirectory = @"Firebase/Network";
-NSString *const kFIRNetworkTempDirectoryName = @"FIRNetworkTemporaryDirectory";
-const NSTimeInterval kFIRNetworkTempFolderExpireTime = 60 * 60;  // 1 hour
-const NSTimeInterval kFIRNetworkTimeOutInterval = 60;            // 1 minute.
-NSString *const kFIRNetworkReachabilityHost = @"app-measurement.com";
-NSString *const kFIRNetworkErrorContext = @"Context";
-
-const int kFIRNetworkHTTPStatusOK = 200;
-const int kFIRNetworkHTTPStatusNoContent = 204;
-const int kFIRNetworkHTTPStatusCodeMultipleChoices = 300;
-const int kFIRNetworkHTTPStatusCodeMovedPermanently = 301;
-const int kFIRNetworkHTTPStatusCodeFound = 302;
-const int kFIRNetworkHTTPStatusCodeNotModified = 304;
-const int kFIRNetworkHTTPStatusCodeMovedTemporarily = 307;
-const int kFIRNetworkHTTPStatusCodeNotFound = 404;
-const int kFIRNetworkHTTPStatusCodeCannotAcceptTraffic = 429;
-const int kFIRNetworkHTTPStatusCodeUnavailable = 503;
-
-NSString *const kFIRNetworkErrorDomain = @"com.firebase.network.ErrorDomain";
diff --git a/Firebase/Core/FIRVersion.m b/Firebase/Core/FIRVersion.m
index 97cd1bc..ec0f6ba 100644
--- a/Firebase/Core/FIRVersion.m
+++ b/Firebase/Core/FIRVersion.m
@@ -29,5 +29,5 @@
 #define STR(x) STR_EXPAND(x)
 #define STR_EXPAND(x) #x
 
-const unsigned char *const FIRVersionString = (const unsigned char *const)STR(Firebase_VERSION);
-const unsigned char *const FIRCoreVersionString = (const unsigned char *const)STR(FIRCore_VERSION);
+const char *const FIRVersionString = (const char *const)STR(Firebase_VERSION);
+const char *const FIRCoreVersionString = (const char *const)STR(FIRCore_VERSION);
diff --git a/Firebase/Core/Private/FIRNetworkMessageCode.h b/Firebase/Core/Private/FIRNetworkMessageCode.h
deleted file mode 100644
index 30f562f..0000000
--- a/Firebase/Core/Private/FIRNetworkMessageCode.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * Copyright 2017 Google
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-// Make sure these codes do not overlap with any contained in the FIRAMessageCode enum.
-typedef NS_ENUM(NSInteger, FIRNetworkMessageCode) {
-  // FIRNetwork.m
-  kFIRNetworkMessageCodeNetwork000 = 900000,  // I-NET900000
-  kFIRNetworkMessageCodeNetwork001 = 900001,  // I-NET900001
-  kFIRNetworkMessageCodeNetwork002 = 900002,  // I-NET900002
-  kFIRNetworkMessageCodeNetwork003 = 900003,  // I-NET900003
-  // FIRNetworkURLSession.m
-  kFIRNetworkMessageCodeURLSession000 = 901000,  // I-NET901000
-  kFIRNetworkMessageCodeURLSession001 = 901001,  // I-NET901001
-  kFIRNetworkMessageCodeURLSession002 = 901002,  // I-NET901002
-  kFIRNetworkMessageCodeURLSession003 = 901003,  // I-NET901003
-  kFIRNetworkMessageCodeURLSession004 = 901004,  // I-NET901004
-  kFIRNetworkMessageCodeURLSession005 = 901005,  // I-NET901005
-  kFIRNetworkMessageCodeURLSession006 = 901006,  // I-NET901006
-  kFIRNetworkMessageCodeURLSession007 = 901007,  // I-NET901007
-  kFIRNetworkMessageCodeURLSession008 = 901008,  // I-NET901008
-  kFIRNetworkMessageCodeURLSession009 = 901009,  // I-NET901009
-  kFIRNetworkMessageCodeURLSession010 = 901010,  // I-NET901010
-  kFIRNetworkMessageCodeURLSession011 = 901011,  // I-NET901011
-  kFIRNetworkMessageCodeURLSession012 = 901012,  // I-NET901012
-  kFIRNetworkMessageCodeURLSession013 = 901013,  // I-NET901013
-  kFIRNetworkMessageCodeURLSession014 = 901014,  // I-NET901014
-  kFIRNetworkMessageCodeURLSession015 = 901015,  // I-NET901015
-  kFIRNetworkMessageCodeURLSession016 = 901016,  // I-NET901016
-  kFIRNetworkMessageCodeURLSession017 = 901017,  // I-NET901017
-  kFIRNetworkMessageCodeURLSession018 = 901018,  // I-NET901018
-  // FIRReachabilityChecker.m
-  kFIRNetworkMessageCodeReachabilityChecker000 = 902000,  // I-NET902000
-  kFIRNetworkMessageCodeReachabilityChecker001 = 902001,  // I-NET902001
-  kFIRNetworkMessageCodeReachabilityChecker002 = 902002,  // I-NET902002
-  kFIRNetworkMessageCodeReachabilityChecker003 = 902003,  // I-NET902003
-  kFIRNetworkMessageCodeReachabilityChecker004 = 902004,  // I-NET902004
-  kFIRNetworkMessageCodeReachabilityChecker005 = 902005,  // I-NET902005
-  kFIRNetworkMessageCodeReachabilityChecker006 = 902006,  // I-NET902006
-};
diff --git a/Firebase/Core/Private/FIRVersion.h b/Firebase/Core/Private/FIRVersion.h
index cec0994..226efb1 100644
--- a/Firebase/Core/Private/FIRVersion.h
+++ b/Firebase/Core/Private/FIRVersion.h
@@ -17,7 +17,7 @@
 #import <Foundation/Foundation.h>
 
 /** The version of the Firebase SDK. */
-FOUNDATION_EXPORT const unsigned char *const FIRVersionString;
+FOUNDATION_EXPORT const char *const FIRVersionString;
 
 /** The version of the FirebaseCore Component. */
-FOUNDATION_EXPORT const unsigned char *const FIRCoreVersionString;
+FOUNDATION_EXPORT const char *const FIRCoreVersionString;
diff --git a/Firebase/Core/Public/FIRLoggerLevel.h b/Firebase/Core/Public/FIRLoggerLevel.h
index 8b6579f..e17e338 100644
--- a/Firebase/Core/Public/FIRLoggerLevel.h
+++ b/Firebase/Core/Public/FIRLoggerLevel.h
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// Note that importing GULLoggerLevel.h will lead to a non-modular header
+// import error.
+
 /**
  * The log levels used by internal logging.
  */
diff --git a/Firebase/Messaging/FIRMessaging.m b/Firebase/Messaging/FIRMessaging.m
index 1152032..5dd7004 100644
--- a/Firebase/Messaging/FIRMessaging.m
+++ b/Firebase/Messaging/FIRMessaging.m
@@ -37,8 +37,8 @@
 #import "FIRMessagingVersionUtilities.h"
 
 #import <FirebaseCore/FIRAppInternal.h>
-#import <FirebaseCore/FIRReachabilityChecker.h>
 #import <FirebaseInstanceID/FirebaseInstanceID.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
 
 #import "NSError+FIRMessaging.h"
 
@@ -125,7 +125,7 @@ NSString *const kFIRMessagingPlistAutoInitEnabled =
 @end
 
 @interface FIRMessaging ()<FIRMessagingClientDelegate, FIRMessagingReceiverDelegate,
-                           FIRReachabilityDelegate>
+                           GULReachabilityDelegate>
 
 // FIRApp properties
 @property(nonatomic, readwrite, strong) NSData *apnsTokenData;
@@ -136,7 +136,7 @@ NSString *const kFIRMessagingPlistAutoInitEnabled =
 @property(nonatomic, readwrite, assign) BOOL isClientSetup;
 
 @property(nonatomic, readwrite, strong) FIRMessagingClient *client;
-@property(nonatomic, readwrite, strong) FIRReachabilityChecker *reachability;
+@property(nonatomic, readwrite, strong) GULReachabilityChecker *reachability;
 @property(nonatomic, readwrite, strong) FIRMessagingDataMessageManager *dataMessageManager;
 @property(nonatomic, readwrite, strong) FIRMessagingPubSub *pubsub;
 @property(nonatomic, readwrite, strong) FIRMessagingRmqManager *rmq2Manager;
@@ -200,8 +200,7 @@ NSString *const kFIRMessagingPlistAutoInitEnabled =
   [self setupReceiver];
 
   NSString *hostname = kFIRMessagingReachabilityHostname;
-  self.reachability = [[FIRReachabilityChecker alloc] initWithReachabilityDelegate:self
-                                                                    loggerDelegate:nil
+  self.reachability = [[GULReachabilityChecker alloc] initWithReachabilityDelegate:self
                                                                           withHost:hostname];
   [self.reachability start];
 
@@ -800,10 +799,10 @@ NSString *const kFIRMessagingPlistAutoInitEnabled =
   }
 }
 
-#pragma mark - FIRReachabilityDelegate
+#pragma mark - GULReachabilityDelegate
 
-- (void)reachability:(FIRReachabilityChecker *)reachability
-       statusChanged:(FIRReachabilityStatus)status {
+- (void)reachability:(GULReachabilityChecker *)reachability
+       statusChanged:(GULReachabilityStatus)status {
   [self onNetworkStatusChanged];
 }
 
@@ -821,15 +820,15 @@ NSString *const kFIRMessagingPlistAutoInitEnabled =
 }
 
 - (BOOL)isNetworkAvailable {
-  FIRReachabilityStatus status = self.reachability.reachabilityStatus;
-  return (status == kFIRReachabilityViaCellular || status == kFIRReachabilityViaWifi);
+  GULReachabilityStatus status = self.reachability.reachabilityStatus;
+  return (status == kGULReachabilityViaCellular || status == kGULReachabilityViaWifi);
 }
 
 - (FIRMessagingNetworkStatus)networkType {
-  FIRReachabilityStatus status = self.reachability.reachabilityStatus;
+  GULReachabilityStatus status = self.reachability.reachabilityStatus;
   if (![self isNetworkAvailable]) {
     return kFIRMessagingReachabilityNotReachable;
-  } else if (status == kFIRReachabilityViaCellular) {
+  } else if (status == kGULReachabilityViaCellular) {
     return kFIRMessagingReachabilityReachableViaWWAN;
   } else {
     return kFIRMessagingReachabilityReachableViaWiFi;
diff --git a/Firebase/Messaging/FIRMessagingClient.h b/Firebase/Messaging/FIRMessagingClient.h
index cb76e98..98337a3 100644
--- a/Firebase/Messaging/FIRMessagingClient.h
+++ b/Firebase/Messaging/FIRMessagingClient.h
@@ -16,7 +16,7 @@
 
 #import "FIRMessaging.h"
 
-@class FIRReachabilityChecker;
+@class GULReachabilityChecker;
 @class GPBMessage;
 
 @class FIRMessagingConnection;
@@ -48,7 +48,7 @@ typedef void(^FIRMessagingConnectCompletionHandler)(NSError *error);
 
 // Designated initializer
 - (instancetype)initWithDelegate:(id<FIRMessagingClientDelegate>)delegate
-                    reachability:(FIRReachabilityChecker *)reachability
+                    reachability:(GULReachabilityChecker *)reachability
                      rmq2Manager:(FIRMessagingRmqManager *)rmq2Manager;
 
 - (void)teardown;
diff --git a/Firebase/Messaging/FIRMessagingClient.m b/Firebase/Messaging/FIRMessagingClient.m
index 0bfb5a8..9d8c558 100644
--- a/Firebase/Messaging/FIRMessagingClient.m
+++ b/Firebase/Messaging/FIRMessagingClient.m
@@ -16,7 +16,7 @@
 
 #import "FIRMessagingClient.h"
 
-#import <FirebaseCore/FIRReachabilityChecker.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
 
 #import "FIRMessaging.h"
 #import "FIRMessagingConnection.h"
@@ -82,7 +82,7 @@ static NSUInteger FIRMessagingServerPort() {
 
 // FIRMessagingService owns these instances
 @property(nonatomic, readwrite, weak) FIRMessagingRmqManager *rmq2Manager;
-@property(nonatomic, readwrite, weak) FIRReachabilityChecker *reachability;
+@property(nonatomic, readwrite, weak) GULReachabilityChecker *reachability;
 
 @property(nonatomic, readwrite, assign) int64_t lastConnectedTimestamp;
 @property(nonatomic, readwrite, assign) int64_t lastDisconnectedTimestamp;
@@ -111,7 +111,7 @@ static NSUInteger FIRMessagingServerPort() {
 }
 
 - (instancetype)initWithDelegate:(id<FIRMessagingClientDelegate>)delegate
-                    reachability:(FIRReachabilityChecker *)reachability
+                    reachability:(GULReachabilityChecker *)reachability
                      rmq2Manager:(FIRMessagingRmqManager *)rmq2Manager {
   self = [super init];
   if (self) {
@@ -471,8 +471,8 @@ static NSUInteger FIRMessagingServerPort() {
 #pragma mark - Schedulers
 
 - (void)scheduleConnectRetry {
-  FIRReachabilityStatus status = self.reachability.reachabilityStatus;
-  BOOL isReachable = (status == kFIRReachabilityViaWifi || status == kFIRReachabilityViaCellular);
+  GULReachabilityStatus status = self.reachability.reachabilityStatus;
+  BOOL isReachable = (status == kGULReachabilityViaWifi || status == kGULReachabilityViaCellular);
   if (!isReachable) {
     FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient010,
                             @"Internet not reachable when signing into MCS during a retry");
diff --git a/Firebase/Core/third_party/FIRAppEnvironmentUtil.h b/Firebase/Utilities/Environment/third_party/GULAppEnvironmentUtil.h
index 09ee504..5b56271 100644
--- a/Firebase/Core/third_party/FIRAppEnvironmentUtil.h
+++ b/Firebase/Utilities/Environment/third_party/GULAppEnvironmentUtil.h
@@ -16,7 +16,7 @@
 
 #import <Foundation/Foundation.h>
 
-@interface FIRAppEnvironmentUtil : NSObject
+@interface GULAppEnvironmentUtil : NSObject
 
 /// Indicates whether the app is from Apple Store or not. Returns NO if the app is on simulator,
 /// development environment or sideloaded.
diff --git a/Firebase/Core/third_party/FIRAppEnvironmentUtil.m b/Firebase/Utilities/Environment/third_party/GULAppEnvironmentUtil.m
index be4e971..e96ba70 100644
--- a/Firebase/Core/third_party/FIRAppEnvironmentUtil.m
+++ b/Firebase/Utilities/Environment/third_party/GULAppEnvironmentUtil.m
@@ -12,10 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#import <Foundation/Foundation.h>
-
-#import "FIRAppEnvironmentUtil.h"
+#import "GULAppEnvironmentUtil.h"
 
+#import <Foundation/Foundation.h>
 #import <dlfcn.h>
 #import <mach-o/dyld.h>
 #import <sys/utsname.h>
@@ -34,7 +33,7 @@ struct encryption_info_command {
 };
 #endif
 
-@implementation FIRAppEnvironmentUtil
+@implementation GULAppEnvironmentUtil
 
 /// A key for the Info.plist to enable or disable checking if the App Store is running in a sandbox.
 /// This will affect your data integrity when using Firebase Analytics, as it will disable some
@@ -81,7 +80,7 @@ static NSString *const kFIRAIdentitySandboxReceiptFileName = @"sandboxReceipt";
 /// AppSync or similar to disable codesignature checks.
 ///
 /// More information at <a href="http://landonf.org/2009/02/index.html">Landon Fuller's blog</a>
-static BOOL isAppEncrypted() {
+static BOOL IsAppEncrypted() {
   const struct mach_header *executableHeader = NULL;
   for (uint32_t i = 0; i < _dyld_image_count(); i++) {
     const struct mach_header *header = _dyld_get_image_header(i);
@@ -125,26 +124,44 @@ static BOOL isAppEncrypted() {
   return NO;
 }
 
+static BOOL HasSCInfoFolder() {
+#if TARGET_OS_IOS || TARGET_OS_TV
+  NSString *bundlePath = [NSBundle mainBundle].bundlePath;
+  NSString *scInfoPath = [bundlePath stringByAppendingPathComponent:@"SC_Info"];
+  return [[NSFileManager defaultManager] fileExistsAtPath:scInfoPath];
+#elif TARGET_OS_OSX
+  return NO;
+#endif
+}
+
+static BOOL HasEmbeddedMobileProvision() {
+#if TARGET_OS_IOS || TARGET_OS_TV
+  return [[NSBundle mainBundle] pathForResource:@"embedded" ofType:@"mobileprovision"].length > 0;
+#elif TARGET_OS_OSX
+  return NO;
+#endif
+}
+
 + (BOOL)isFromAppStore {
   static dispatch_once_t isEncryptedOnce;
   static BOOL isEncrypted = NO;
 
   dispatch_once(&isEncryptedOnce, ^{
-    isEncrypted = isAppEncrypted();
+    isEncrypted = IsAppEncrypted();
   });
 
-  if ([FIRAppEnvironmentUtil isSimulator]) {
+  if ([GULAppEnvironmentUtil isSimulator]) {
     return NO;
   }
 
   // If an app contain the sandboxReceipt file, it means its coming from TestFlight
   // This must be checked before the SCInfo Folder check below since TestFlight apps may
   // also have an SCInfo folder.
-  if ([FIRAppEnvironmentUtil isAppStoreReceiptSandbox]) {
+  if ([GULAppEnvironmentUtil isAppStoreReceiptSandbox]) {
     return NO;
   }
 
-  if ([FIRAppEnvironmentUtil hasSCInfoFolder]) {
+  if (HasSCInfoFolder()) {
     // When iTunes downloads a .ipa, it also gets a customized .sinf file which is added to the
     // main SC_Info directory.
     return YES;
@@ -154,7 +171,7 @@ static BOOL isAppEncrypted() {
   // the iTunesMetadata.plist outside of the sandbox will be rejected by Apple.
   // If the app does not contain the embedded.mobileprovision which is stripped out by Apple when
   // the app is submitted to store, then it is highly likely that it is from Apple Store.
-  return isEncrypted && ![FIRAppEnvironmentUtil hasEmbeddedMobileProvision];
+  return isEncrypted && !HasEmbeddedMobileProvision();
 }
 
 + (BOOL)isAppStoreReceiptSandbox {
@@ -172,17 +189,9 @@ static BOOL isAppEncrypted() {
   return [appStoreReceiptFileName isEqualToString:kFIRAIdentitySandboxReceiptFileName];
 }
 
-+ (BOOL)hasEmbeddedMobileProvision {
-#if TARGET_OS_IOS || TARGET_OS_TV
-  return [[NSBundle mainBundle] pathForResource:@"embedded" ofType:@"mobileprovision"].length > 0;
-#elif TARGET_OS_OSX
-  return NO;
-#endif
-}
-
 + (BOOL)isSimulator {
 #if TARGET_OS_IOS || TARGET_OS_TV
-  NSString *platform = [FIRAppEnvironmentUtil deviceModel];
+  NSString *platform = [GULAppEnvironmentUtil deviceModel];
   return [platform isEqual:@"x86_64"] || [platform isEqual:@"i386"];
 #elif TARGET_OS_OSX
   return NO;
@@ -224,16 +233,4 @@ static BOOL isAppEncrypted() {
 #endif
 }
 
-#pragma mark - Helper methods
-
-+ (BOOL)hasSCInfoFolder {
-#if TARGET_OS_IOS || TARGET_OS_TV
-  NSString *bundlePath = [NSBundle mainBundle].bundlePath;
-  NSString *scInfoPath = [bundlePath stringByAppendingPathComponent:@"SC_Info"];
-  return [[NSFileManager defaultManager] fileExistsAtPath:scInfoPath];
-#elif TARGET_OS_OSX
-  return NO;
-#endif
-}
-
 @end
diff --git a/Firebase/Utilities/Logger/GULLogger.m b/Firebase/Utilities/Logger/GULLogger.m
new file mode 100644
index 0000000..5c808ea
--- /dev/null
+++ b/Firebase/Utilities/Logger/GULLogger.m
@@ -0,0 +1,214 @@
+// Copyright 2018 Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "Private/GULLogger.h"
+
+#include <asl.h>
+
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
+#import "Public/GULLoggerLevel.h"
+
+/// Key for the debug mode bit in NSUserDefaults.
+NSString *const kGULPersistedDebugModeKey = @"/google/utilities/debug_mode";
+
+/// ASL client facility name used by GULLogger.
+const char *kGULLoggerASLClientFacilityName = "com.google.utilities.logger";
+
+static dispatch_once_t sGULLoggerOnceToken;
+
+static aslclient sGULLoggerClient;
+
+static dispatch_queue_t sGULClientQueue;
+
+static BOOL sGULLoggerDebugMode;
+
+static GULLoggerLevel sGULLoggerMaximumLevel;
+
+// Allow clients to register a version to include in the log.
+static const char *sVersion = "";
+
+static GULLoggerService kGULLoggerLogger = @"[GULLogger]";
+
+#ifdef DEBUG
+/// The regex pattern for the message code.
+static NSString *const kMessageCodePattern = @"^I-[A-Z]{3}[0-9]{6}$";
+static NSRegularExpression *sMessageCodeRegex;
+#endif
+
+void GULLoggerInitializeASL(BOOL overrideSTDERR, BOOL forceDebugMode) {
+  dispatch_once(&sGULLoggerOnceToken, ^{
+    NSInteger majorOSVersion = [[GULAppEnvironmentUtil systemVersion] integerValue];
+    uint32_t aslOptions = ASL_OPT_STDERR;
+#if TARGET_OS_SIMULATOR
+    // The iOS 11 simulator doesn't need the ASL_OPT_STDERR flag.
+    if (majorOSVersion >= 11) {
+      aslOptions = 0;
+    }
+#else
+    // Devices running iOS 10 or higher don't need the ASL_OPT_STDERR flag.
+    if (majorOSVersion >= 10) {
+      aslOptions = 0;
+    }
+#endif  // TARGET_OS_SIMULATOR
+
+    // Override the aslOptions to ASL_OPT_STDERR if the override argument is passed in.
+    if (overrideSTDERR) {
+      aslOptions = ASL_OPT_STDERR;
+    }
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"  // asl is deprecated
+    // Initialize the ASL client handle.
+    sGULLoggerClient = asl_open(NULL, kGULLoggerASLClientFacilityName, aslOptions);
+    sGULLoggerDebugMode = forceDebugMode;
+    sGULLoggerMaximumLevel = GULLoggerLevelNotice;
+
+    if (forceDebugMode) {
+      asl_set_filter(sGULLoggerClient, ASL_FILTER_MASK_UPTO(ASL_LEVEL_DEBUG));
+    } else {
+      // Set the filter used by system/device log. Initialize in default mode.
+      asl_set_filter(sGULLoggerClient, ASL_FILTER_MASK_UPTO(ASL_LEVEL_NOTICE));
+    }
+
+    // We should disable debug mode if we are running from App Store.
+    if (sGULLoggerDebugMode && [GULAppEnvironmentUtil isFromAppStore]) {
+      sGULLoggerDebugMode = NO;
+    }
+
+    sGULClientQueue = dispatch_queue_create("GULLoggingClientQueue", DISPATCH_QUEUE_SERIAL);
+    dispatch_set_target_queue(sGULClientQueue,
+                              dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0));
+
+#ifdef DEBUG
+    sMessageCodeRegex =
+        [NSRegularExpression regularExpressionWithPattern:kMessageCodePattern options:0 error:NULL];
+#endif
+  });
+}
+
+void GULSetLoggerLevel(GULLoggerLevel loggerLevel) {
+  if (loggerLevel < GULLoggerLevelMin || loggerLevel > GULLoggerLevelMax) {
+    GULLogError(kGULLoggerLogger, NO, @"I-COR000023", @"Invalid logger level, %ld",
+                (long)loggerLevel);
+    return;
+  }
+  GULLoggerInitializeASL(NO, NO);
+  // We should not raise the logger level if we are running from App Store.
+  if (loggerLevel >= GULLoggerLevelNotice && [GULAppEnvironmentUtil isFromAppStore]) {
+    return;
+  }
+
+  sGULLoggerMaximumLevel = loggerLevel;
+  dispatch_async(sGULClientQueue, ^{
+    asl_set_filter(sGULLoggerClient, ASL_FILTER_MASK_UPTO(loggerLevel));
+  });
+}
+
+/**
+ * Check if the level is high enough to be loggable.
+ */
+__attribute__((no_sanitize("thread"))) BOOL GULIsLoggableLevel(GULLoggerLevel loggerLevel) {
+  GULLoggerInitializeASL(NO, NO);
+  if (sGULLoggerDebugMode) {
+    return YES;
+  }
+  return (BOOL)(loggerLevel <= sGULLoggerMaximumLevel);
+}
+
+#ifdef DEBUG
+void GULResetLogger() {
+  sGULLoggerOnceToken = 0;
+}
+
+aslclient getGULLoggerClient() {
+  return sGULLoggerClient;
+}
+
+dispatch_queue_t getGULClientQueue() {
+  return sGULClientQueue;
+}
+
+BOOL getGULLoggerDebugMode() {
+  return sGULLoggerDebugMode;
+}
+#endif
+
+void GULLoggerRegisterVersion(const char *version) {
+  sVersion = version;
+}
+
+void GULLogBasic(GULLoggerLevel level,
+                 GULLoggerService service,
+                 BOOL forceLog,
+                 NSString *messageCode,
+                 NSString *message,
+                 va_list args_ptr) {
+  GULLoggerInitializeASL(NO, NO);
+  if (!(level <= sGULLoggerMaximumLevel || sGULLoggerDebugMode || forceLog)) {
+    return;
+  }
+
+#ifdef DEBUG
+  NSCAssert(messageCode.length == 11, @"Incorrect message code length.");
+  NSRange messageCodeRange = NSMakeRange(0, messageCode.length);
+  NSUInteger numberOfMatches =
+      [sMessageCodeRegex numberOfMatchesInString:messageCode options:0 range:messageCodeRange];
+  NSCAssert(numberOfMatches == 1, @"Incorrect message code format.");
+#endif
+  NSString *logMsg = [[NSString alloc] initWithFormat:message arguments:args_ptr];
+  logMsg = [NSString stringWithFormat:@"%s - %@[%@] %@", sVersion, service, messageCode, logMsg];
+  dispatch_async(sGULClientQueue, ^{
+    asl_log(sGULLoggerClient, NULL, level, "%s", logMsg.UTF8String);
+  });
+}
+#pragma clang diagnostic pop
+
+/**
+ * Generates the logging functions using macros.
+ *
+ * Calling GULLogError(kGULLoggerCore, @"I-COR000001", @"Configure %@ failed.", @"blah") shows:
+ * yyyy-mm-dd hh:mm:ss.SSS sender[PID] <Error> [{service}][I-COR000001] Configure blah failed.
+ * Calling GULLogDebug(kGULLoggerCore, @"I-COR000001", @"Configure succeed.") shows:
+ * yyyy-mm-dd hh:mm:ss.SSS sender[PID] <Debug> [{service}][I-COR000001] Configure succeed.
+ */
+#define GUL_LOGGING_FUNCTION(level)                                                     \
+  void GULLog##level(GULLoggerService service, BOOL force, NSString *messageCode,       \
+                     NSString *message, ...) {                                          \
+    va_list args_ptr;                                                                   \
+    va_start(args_ptr, message);                                                        \
+    GULLogBasic(GULLoggerLevel##level, service, force, messageCode, message, args_ptr); \
+    va_end(args_ptr);                                                                   \
+  }
+
+GUL_LOGGING_FUNCTION(Error)
+GUL_LOGGING_FUNCTION(Warning)
+GUL_LOGGING_FUNCTION(Notice)
+GUL_LOGGING_FUNCTION(Info)
+GUL_LOGGING_FUNCTION(Debug)
+
+#undef GUL_MAKE_LOGGER
+
+#pragma mark - GULLoggerWrapper
+
+@implementation GULLoggerWrapper
+
++ (void)logWithLevel:(GULLoggerLevel)level
+         withService:(GULLoggerService)service
+            withCode:(NSString *)messageCode
+         withMessage:(NSString *)message
+            withArgs:(va_list)args {
+  GULLogBasic(level, service, NO, messageCode, message, args);
+}
+
+@end
diff --git a/Firebase/Utilities/Logger/Private/GULLogger.h b/Firebase/Utilities/Logger/Private/GULLogger.h
new file mode 100644
index 0000000..c8b12e8
--- /dev/null
+++ b/Firebase/Utilities/Logger/Private/GULLogger.h
@@ -0,0 +1,151 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <GoogleUtilities/GULLoggerLevel.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * The services used in the logger.
+ */
+typedef NSString *const GULLoggerService;
+
+#ifdef __cplusplus
+extern "C" {
+#endif  // __cplusplus
+
+/**
+ * Initialize GULLogger.
+ * (required) overrideSTDERR Override the aslOptions to ASL_OPT_STDERR.
+ * (required) forceDebugMode Force the asl level to ASL_LEVEL_DEBUG.
+ */
+extern void GULLoggerInitializeASL(BOOL overrideSTDERR, BOOL forceDebugMode);
+
+/**
+ * Changes the default logging level of GULLoggerLevelNotice to a user-specified level.
+ * The default level cannot be set above GULLoggerLevelNotice if the app is running from App Store.
+ * (required) log level (one of the GULLoggerLevel enum values).
+ */
+extern void GULSetLoggerLevel(GULLoggerLevel loggerLevel);
+
+/**
+ * Checks if the specified logger level is loggable given the current settings.
+ * (required) log level (one of the GULLoggerLevel enum values).
+ */
+extern BOOL GULIsLoggableLevel(GULLoggerLevel loggerLevel);
+
+/**
+ * Register version to include in logs.
+ * (required) version
+ */
+extern void GULLoggerRegisterVersion(const char *version);
+
+/**
+ * Logs a message to the Xcode console and the device log. If running from AppStore, will
+ * not log any messages with a level higher than GULLoggerLevelNotice to avoid log spamming.
+ * (required) log level (one of the GULLoggerLevel enum values).
+ * (required) service name of type GULLoggerService.
+ * (required) message code starting with "I-" which means iOS, followed by a capitalized
+ *            three-character service identifier and a six digit integer message ID that is unique
+ *            within the service.
+ *            An example of the message code is @"I-COR000001".
+ * (required) message string which can be a format string.
+ * (optional) variable arguments list obtained from calling va_start, used when message is a format
+ *            string.
+ */
+extern void GULLogBasic(GULLoggerLevel level,
+                        GULLoggerService service,
+                        BOOL forceLog,
+                        NSString *messageCode,
+                        NSString *message,
+// On 64-bit simulators, va_list is not a pointer, so cannot be marked nullable
+// See: http://stackoverflow.com/q/29095469
+#if __LP64__ && TARGET_OS_SIMULATOR || TARGET_OS_OSX
+                        va_list args_ptr
+#else
+                        va_list _Nullable args_ptr
+#endif
+);
+
+/**
+ * The following functions accept the following parameters in order:
+ * (required) service name of type GULLoggerService.
+ * (required) message code starting from "I-" which means iOS, followed by a capitalized
+ *            three-character service identifier and a six digit integer message ID that is unique
+ *            within the service.
+ *            An example of the message code is @"I-COR000001".
+ *            See go/firebase-log-proposal for details.
+ * (required) message string which can be a format string.
+ * (optional) the list of arguments to substitute into the format string.
+ * Example usage:
+ * GULLogError(kGULLoggerCore, @"I-COR000001", @"Configuration of %@ failed.", app.name);
+ */
+extern void GULLogError(GULLoggerService service,
+                        BOOL force,
+                        NSString *messageCode,
+                        NSString *message,
+                        ...) NS_FORMAT_FUNCTION(4, 5);
+extern void GULLogWarning(GULLoggerService service,
+                          BOOL force,
+                          NSString *messageCode,
+                          NSString *message,
+                          ...) NS_FORMAT_FUNCTION(4, 5);
+extern void GULLogNotice(GULLoggerService service,
+                         BOOL force,
+                         NSString *messageCode,
+                         NSString *message,
+                         ...) NS_FORMAT_FUNCTION(4, 5);
+extern void GULLogInfo(GULLoggerService service,
+                       BOOL force,
+                       NSString *messageCode,
+                       NSString *message,
+                       ...) NS_FORMAT_FUNCTION(4, 5);
+extern void GULLogDebug(GULLoggerService service,
+                        BOOL force,
+                        NSString *messageCode,
+                        NSString *message,
+                        ...) NS_FORMAT_FUNCTION(4, 5);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
+
+@interface GULLoggerWrapper : NSObject
+
+/**
+ * Objective-C wrapper for GULLogBasic to allow weak linking to GULLogger
+ * (required) log level (one of the GULLoggerLevel enum values).
+ * (required) service name of type GULLoggerService.
+ * (required) message code starting with "I-" which means iOS, followed by a capitalized
+ *            three-character service identifier and a six digit integer message ID that is unique
+ *            within the service.
+ *            An example of the message code is @"I-COR000001".
+ * (required) message string which can be a format string.
+ * (optional) variable arguments list obtained from calling va_start, used when message is a format
+ *            string.
+ */
+
++ (void)logWithLevel:(GULLoggerLevel)level
+         withService:(GULLoggerService)service
+            withCode:(NSString *)messageCode
+         withMessage:(NSString *)message
+            withArgs:(va_list)args;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/Firebase/Utilities/Logger/Public/GULLoggerLevel.h b/Firebase/Utilities/Logger/Public/GULLoggerLevel.h
new file mode 100644
index 0000000..09ebf37
--- /dev/null
+++ b/Firebase/Utilities/Logger/Public/GULLoggerLevel.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * The log levels used by internal logging.
+ */
+typedef NS_ENUM(NSInteger, GULLoggerLevel) {
+  /** Error level, matches ASL_LEVEL_ERR. */
+  GULLoggerLevelError = 3,
+  /** Warning level, matches ASL_LEVEL_WARNING. */
+  GULLoggerLevelWarning = 4,
+  /** Notice level, matches ASL_LEVEL_NOTICE. */
+  GULLoggerLevelNotice = 5,
+  /** Info level, matches ASL_LEVEL_NOTICE. */
+  GULLoggerLevelInfo = 6,
+  /** Debug level, matches ASL_LEVEL_DEBUG. */
+  GULLoggerLevelDebug = 7,
+  /** Minimum log level. */
+  GULLoggerLevelMin = GULLoggerLevelError,
+  /** Maximum log level. */
+  GULLoggerLevelMax = GULLoggerLevelDebug
+} NS_SWIFT_NAME(GoogleLoggerLevel);
diff --git a/Firebase/Utilities/NSData+zlib/GULNSData+zlib.h b/Firebase/Utilities/NSData+zlib/GULNSData+zlib.h
new file mode 100644
index 0000000..36f94a7
--- /dev/null
+++ b/Firebase/Utilities/NSData+zlib/GULNSData+zlib.h
@@ -0,0 +1,49 @@
+// Copyright 2018 Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+/// This is a copy of Google Toolbox for Mac library to avoid creating an extra framework.
+
+// NOTE: For 64bit, none of these apis handle input sizes >32bits, they will return nil when given
+// such data. To handle data of that size you really should be streaming it rather then doing it all
+// in memory.
+
+@interface NSData (GULGzip)
+
+/// Returns an data as the result of decompressing the payload of |data|.The data to decompress must
+/// be a gzipped payloads.
++ (NSData *)gul_dataByInflatingGzippedData:(NSData *)data error:(NSError **)error;
+
+/// Returns an compressed data with the result of gzipping the payload of |data|. Uses the default
+/// compression level.
++ (NSData *)gul_dataByGzippingData:(NSData *)data error:(NSError **)error;
+
+FOUNDATION_EXPORT NSString *const GULNSDataZlibErrorDomain;
+FOUNDATION_EXPORT NSString *const GULNSDataZlibErrorKey;           // NSNumber
+FOUNDATION_EXPORT NSString *const GULNSDataZlibRemainingBytesKey;  // NSNumber
+
+typedef NS_ENUM(NSInteger, GULNSDataZlibError) {
+  GULNSDataZlibErrorGreaterThan32BitsToCompress = 1024,
+  // An internal zlib error.
+  // GULNSDataZlibErrorKey will contain the error value.
+  // NSLocalizedDescriptionKey may contain an error string from zlib.
+  // Look in zlib.h for list of errors.
+  GULNSDataZlibErrorInternal,
+  // There was left over data in the buffer that was not used.
+  // GULNSDataZlibRemainingBytesKey will contain number of remaining bytes.
+  GULNSDataZlibErrorDataRemaining
+};
+
+@end
diff --git a/Firebase/Utilities/NSData+zlib/GULNSData+zlib.m b/Firebase/Utilities/NSData+zlib/GULNSData+zlib.m
new file mode 100644
index 0000000..cd3394a
--- /dev/null
+++ b/Firebase/Utilities/NSData+zlib/GULNSData+zlib.m
@@ -0,0 +1,207 @@
+// Copyright 2018 Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "GULNSData+zlib.h"
+
+#import <zlib.h>
+
+#define kChunkSize 1024
+#define Z_DEFAULT_COMPRESSION (-1)
+
+NSString *const GULNSDataZlibErrorDomain = @"com.google.GULNSDataZlibErrorDomain";
+NSString *const GULNSDataZlibErrorKey = @"GULNSDataZlibErrorKey";
+NSString *const GULNSDataZlibRemainingBytesKey = @"GULNSDataZlibRemainingBytesKey";
+
+@implementation NSData (GULGzip)
+
++ (NSData *)gul_dataByInflatingGzippedData:(NSData *)data error:(NSError **)error {
+  const void *bytes = [data bytes];
+  NSUInteger length = [data length];
+  if (!bytes || !length) {
+    return nil;
+  }
+
+#if defined(__LP64__) && __LP64__
+  // Don't support > 32bit length for 64 bit, see note in header.
+  if (length > UINT_MAX) {
+    return nil;
+  }
+#endif
+
+  z_stream strm;
+  bzero(&strm, sizeof(z_stream));
+
+  // Setup the input.
+  strm.avail_in = (unsigned int)length;
+  strm.next_in = (unsigned char *)bytes;
+
+  int windowBits = 15;  // 15 to enable any window size
+  windowBits += 32;     // and +32 to enable zlib or gzip header detection.
+
+  int retCode;
+  if ((retCode = inflateInit2(&strm, windowBits)) != Z_OK) {
+    if (error) {
+      NSDictionary *userInfo = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:retCode]
+                                                           forKey:GULNSDataZlibErrorKey];
+      *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                   code:GULNSDataZlibErrorInternal
+                               userInfo:userInfo];
+    }
+    return nil;
+  }
+
+  // Hint the size at 4x the input size.
+  NSMutableData *result = [NSMutableData dataWithCapacity:(length * 4)];
+  unsigned char output[kChunkSize];
+
+  // Loop to collect the data.
+  do {
+    // Update what we're passing in.
+    strm.avail_out = kChunkSize;
+    strm.next_out = output;
+    retCode = inflate(&strm, Z_NO_FLUSH);
+    if ((retCode != Z_OK) && (retCode != Z_STREAM_END)) {
+      if (error) {
+        NSMutableDictionary *userInfo =
+            [NSMutableDictionary dictionaryWithObject:[NSNumber numberWithInt:retCode]
+                                               forKey:GULNSDataZlibErrorKey];
+        if (strm.msg) {
+          NSString *message = [NSString stringWithUTF8String:strm.msg];
+          if (message) {
+            [userInfo setObject:message forKey:NSLocalizedDescriptionKey];
+          }
+        }
+        *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                     code:GULNSDataZlibErrorInternal
+                                 userInfo:userInfo];
+      }
+      inflateEnd(&strm);
+      return nil;
+    }
+    // Collect what we got.
+    unsigned gotBack = kChunkSize - strm.avail_out;
+    if (gotBack > 0) {
+      [result appendBytes:output length:gotBack];
+    }
+
+  } while (retCode == Z_OK);
+
+  // Make sure there wasn't more data tacked onto the end of a valid compressed stream.
+  if (strm.avail_in != 0) {
+    if (error) {
+      NSDictionary *userInfo =
+          [NSDictionary dictionaryWithObject:[NSNumber numberWithUnsignedInt:strm.avail_in]
+                                      forKey:GULNSDataZlibRemainingBytesKey];
+      *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                   code:GULNSDataZlibErrorDataRemaining
+                               userInfo:userInfo];
+    }
+    result = nil;
+  }
+  // The only way out of the loop was by hitting the end of the stream.
+  NSAssert(retCode == Z_STREAM_END,
+           @"Thought we finished inflate w/o getting a result of stream end, code %d", retCode);
+
+  // Clean up.
+  inflateEnd(&strm);
+
+  return result;
+}
+
++ (NSData *)gul_dataByGzippingData:(NSData *)data error:(NSError **)error {
+  const void *bytes = [data bytes];
+  NSUInteger length = [data length];
+
+  int level = Z_DEFAULT_COMPRESSION;
+  if (!bytes || !length) {
+    return nil;
+  }
+
+#if defined(__LP64__) && __LP64__
+  // Don't support > 32bit length for 64 bit, see note in header.
+  if (length > UINT_MAX) {
+    if (error) {
+      *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                   code:GULNSDataZlibErrorGreaterThan32BitsToCompress
+                               userInfo:nil];
+    }
+    return nil;
+  }
+#endif
+
+  z_stream strm;
+  bzero(&strm, sizeof(z_stream));
+
+  int memLevel = 8;          // Default.
+  int windowBits = 15 + 16;  // Enable gzip header instead of zlib header.
+
+  int retCode;
+  if ((retCode = deflateInit2(&strm, level, Z_DEFLATED, windowBits, memLevel,
+                              Z_DEFAULT_STRATEGY)) != Z_OK) {
+    if (error) {
+      NSDictionary *userInfo = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:retCode]
+                                                           forKey:GULNSDataZlibErrorKey];
+      *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                   code:GULNSDataZlibErrorInternal
+                               userInfo:userInfo];
+    }
+    return nil;
+  }
+
+  // Hint the size at 1/4 the input size.
+  NSMutableData *result = [NSMutableData dataWithCapacity:(length / 4)];
+  unsigned char output[kChunkSize];
+
+  // Setup the input.
+  strm.avail_in = (unsigned int)length;
+  strm.next_in = (unsigned char *)bytes;
+
+  // Collect the data.
+  do {
+    // update what we're passing in
+    strm.avail_out = kChunkSize;
+    strm.next_out = output;
+    retCode = deflate(&strm, Z_FINISH);
+    if ((retCode != Z_OK) && (retCode != Z_STREAM_END)) {
+      if (error) {
+        NSDictionary *userInfo = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:retCode]
+                                                             forKey:GULNSDataZlibErrorKey];
+        *error = [NSError errorWithDomain:GULNSDataZlibErrorDomain
+                                     code:GULNSDataZlibErrorInternal
+                                 userInfo:userInfo];
+      }
+      deflateEnd(&strm);
+      return nil;
+    }
+    // Collect what we got.
+    unsigned gotBack = kChunkSize - strm.avail_out;
+    if (gotBack > 0) {
+      [result appendBytes:output length:gotBack];
+    }
+
+  } while (retCode == Z_OK);
+
+  // If the loop exits, it used all input and the stream ended.
+  NSAssert(strm.avail_in == 0,
+           @"Should have finished deflating without using all input, %u bytes left", strm.avail_in);
+  NSAssert(retCode == Z_STREAM_END,
+           @"thought we finished deflate w/o getting a result of stream end, code %d", retCode);
+
+  // Clean up.
+  deflateEnd(&strm);
+
+  return result;
+}
+
+@end
diff --git a/Firebase/Core/FIRMutableDictionary.m b/Firebase/Utilities/Network/GULMutableDictionary.m
index 31941bc..d281eb4 100644
--- a/Firebase/Core/FIRMutableDictionary.m
+++ b/Firebase/Utilities/Network/GULMutableDictionary.m
@@ -12,9 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#import "Private/FIRMutableDictionary.h"
+#import "Private/GULMutableDictionary.h"
 
-@implementation FIRMutableDictionary {
+@implementation GULMutableDictionary {
   /// The mutable dictionary.
   NSMutableDictionary *_objects;
 
@@ -28,7 +28,7 @@
 
   if (self) {
     _objects = [[NSMutableDictionary alloc] init];
-    _queue = dispatch_queue_create("FIRMutableDictionary", DISPATCH_QUEUE_SERIAL);
+    _queue = dispatch_queue_create("GULMutableDictionary", DISPATCH_QUEUE_SERIAL);
   }
 
   return self;
diff --git a/Firebase/Core/FIRNetwork.m b/Firebase/Utilities/Network/GULNetwork.m
index ff292fc..233500b 100644
--- a/Firebase/Core/FIRNetwork.m
+++ b/Firebase/Utilities/Network/GULNetwork.m
@@ -12,68 +12,66 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#import "Private/FIRNetwork.h"
-#import "Private/FIRNetworkMessageCode.h"
+#import "Private/GULNetwork.h"
+#import "Private/GULNetworkMessageCode.h"
 
-#import "Private/FIRLogger.h"
-#import "Private/FIRMutableDictionary.h"
-#import "Private/FIRNetworkConstants.h"
-#import "Private/FIRReachabilityChecker.h"
-
-#import <GoogleToolboxForMac/GTMNSData+zlib.h>
+#import <GoogleUtilities/GULLogger.h>
+#import <GoogleUtilities/GULNSData+zlib.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
+#import "Private/GULMutableDictionary.h"
+#import "Private/GULNetworkConstants.h"
 
 /// Constant string for request header Content-Encoding.
-static NSString *const kFIRNetworkContentCompressionKey = @"Content-Encoding";
+static NSString *const kGULNetworkContentCompressionKey = @"Content-Encoding";
 
 /// Constant string for request header Content-Encoding value.
-static NSString *const kFIRNetworkContentCompressionValue = @"gzip";
+static NSString *const kGULNetworkContentCompressionValue = @"gzip";
 
 /// Constant string for request header Content-Length.
-static NSString *const kFIRNetworkContentLengthKey = @"Content-Length";
+static NSString *const kGULNetworkContentLengthKey = @"Content-Length";
 
 /// Constant string for request header Content-Type.
-static NSString *const kFIRNetworkContentTypeKey = @"Content-Type";
+static NSString *const kGULNetworkContentTypeKey = @"Content-Type";
 
 /// Constant string for request header Content-Type value.
-static NSString *const kFIRNetworkContentTypeValue = @"application/x-www-form-urlencoded";
+static NSString *const kGULNetworkContentTypeValue = @"application/x-www-form-urlencoded";
 
 /// Constant string for GET request method.
-static NSString *const kFIRNetworkGETRequestMethod = @"GET";
+static NSString *const kGULNetworkGETRequestMethod = @"GET";
 
 /// Constant string for POST request method.
-static NSString *const kFIRNetworkPOSTRequestMethod = @"POST";
+static NSString *const kGULNetworkPOSTRequestMethod = @"POST";
 
 /// Default constant string as a prefix for network logger.
-static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
+static NSString *const kGULNetworkLogTag = @"Google/Utilities/Network";
 
-@interface FIRNetwork () <FIRReachabilityDelegate, FIRNetworkLoggerDelegate>
+@interface GULNetwork () <GULReachabilityDelegate, GULNetworkLoggerDelegate>
 @end
 
-@implementation FIRNetwork {
+@implementation GULNetwork {
   /// Network reachability.
-  FIRReachabilityChecker *_reachability;
+  GULReachabilityChecker *_reachability;
 
   /// The dictionary of requests by session IDs { NSString : id }.
-  FIRMutableDictionary *_requests;
+  GULMutableDictionary *_requests;
 }
 
 - (instancetype)init {
-  return [self initWithReachabilityHost:kFIRNetworkReachabilityHost];
+  return [self initWithReachabilityHost:kGULNetworkReachabilityHost];
 }
 
 - (instancetype)initWithReachabilityHost:(NSString *)reachabilityHost {
   self = [super init];
   if (self) {
     // Setup reachability.
-    _reachability = [[FIRReachabilityChecker alloc] initWithReachabilityDelegate:self
-                                                                  loggerDelegate:self
+    _reachability = [[GULReachabilityChecker alloc] initWithReachabilityDelegate:self
                                                                         withHost:reachabilityHost];
     if (![_reachability start]) {
       return nil;
     }
 
-    _requests = [[FIRMutableDictionary alloc] init];
-    _timeoutInterval = kFIRNetworkTimeOutInterval;
+    _requests = [[GULMutableDictionary alloc] init];
+    _timeoutInterval = kGULNetworkTimeOutInterval;
   }
   return self;
 }
@@ -86,8 +84,8 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
 #pragma mark - External Methods
 
 + (void)handleEventsForBackgroundURLSessionID:(NSString *)sessionID
-                            completionHandler:(FIRNetworkSystemCompletionHandler)completionHandler {
-  [FIRNetworkURLSession handleEventsForBackgroundURLSessionID:sessionID
+                            completionHandler:(GULNetworkSystemCompletionHandler)completionHandler {
+  [GULNetworkURLSession handleEventsForBackgroundURLSessionID:sessionID
                                             completionHandler:completionHandler];
 }
 
@@ -95,13 +93,13 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
                    payload:(NSData *)payload
                      queue:(dispatch_queue_t)queue
     usingBackgroundSession:(BOOL)usingBackgroundSession
-         completionHandler:(FIRNetworkCompletionHandler)handler {
+         completionHandler:(GULNetworkCompletionHandler)handler {
   if (!url.absoluteString.length) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkInvalidURL queue:queue withHandler:handler];
+    [self handleErrorWithCode:GULErrorCodeNetworkInvalidURL queue:queue withHandler:handler];
     return nil;
   }
 
-  NSTimeInterval timeOutInterval = _timeoutInterval ?: kFIRNetworkTimeOutInterval;
+  NSTimeInterval timeOutInterval = _timeoutInterval ?: kGULNetworkTimeOutInterval;
 
   NSMutableURLRequest *request =
       [[NSMutableURLRequest alloc] initWithURL:url
@@ -109,18 +107,18 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
                                timeoutInterval:timeOutInterval];
 
   if (!request) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkSessionTaskCreation
+    [self handleErrorWithCode:GULErrorCodeNetworkSessionTaskCreation
                         queue:queue
                   withHandler:handler];
     return nil;
   }
 
   NSError *compressError = nil;
-  NSData *compressedData = [NSData gtm_dataByGzippingData:payload error:&compressError];
+  NSData *compressedData = [NSData gul_dataByGzippingData:payload error:&compressError];
   if (!compressedData || compressError) {
     if (compressError || payload.length > 0) {
       // If the payload is not empty but it fails to compress the payload, something has been wrong.
-      [self handleErrorWithCode:FIRErrorCodeNetworkPayloadCompression
+      [self handleErrorWithCode:GULErrorCodeNetworkPayloadCompression
                           queue:queue
                     withHandler:handler];
       return nil;
@@ -131,22 +129,22 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
   NSString *postLength = @(compressedData.length).stringValue;
 
   // Set up the request with the compressed data.
-  [request setValue:postLength forHTTPHeaderField:kFIRNetworkContentLengthKey];
+  [request setValue:postLength forHTTPHeaderField:kGULNetworkContentLengthKey];
   request.HTTPBody = compressedData;
-  request.HTTPMethod = kFIRNetworkPOSTRequestMethod;
-  [request setValue:kFIRNetworkContentTypeValue forHTTPHeaderField:kFIRNetworkContentTypeKey];
-  [request setValue:kFIRNetworkContentCompressionValue
-      forHTTPHeaderField:kFIRNetworkContentCompressionKey];
+  request.HTTPMethod = kGULNetworkPOSTRequestMethod;
+  [request setValue:kGULNetworkContentTypeValue forHTTPHeaderField:kGULNetworkContentTypeKey];
+  [request setValue:kGULNetworkContentCompressionValue
+      forHTTPHeaderField:kGULNetworkContentCompressionKey];
 
-  FIRNetworkURLSession *fetcher = [[FIRNetworkURLSession alloc] initWithNetworkLoggerDelegate:self];
+  GULNetworkURLSession *fetcher = [[GULNetworkURLSession alloc] initWithNetworkLoggerDelegate:self];
   fetcher.backgroundNetworkEnabled = usingBackgroundSession;
 
-  __weak FIRNetwork *weakSelf = self;
+  __weak GULNetwork *weakSelf = self;
   NSString *requestID = [fetcher
       sessionIDFromAsyncPOSTRequest:request
                   completionHandler:^(NSHTTPURLResponse *response, NSData *data,
                                       NSString *sessionID, NSError *error) {
-                    FIRNetwork *strongSelf = weakSelf;
+                    GULNetwork *strongSelf = weakSelf;
                     if (!strongSelf) {
                       return;
                     }
@@ -161,14 +159,14 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
                     });
                   }];
   if (!requestID) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkSessionTaskCreation
+    [self handleErrorWithCode:GULErrorCodeNetworkSessionTaskCreation
                         queue:queue
                   withHandler:handler];
     return nil;
   }
 
-  [self firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                    messageCode:kFIRNetworkMessageCodeNetwork000
+  [self GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                    messageCode:kGULNetworkMessageCodeNetwork000
                         message:@"Uploading data. Host"
                         context:url];
   _requests[requestID] = fetcher;
@@ -179,37 +177,37 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
                    headers:(NSDictionary *)headers
                      queue:(dispatch_queue_t)queue
     usingBackgroundSession:(BOOL)usingBackgroundSession
-         completionHandler:(FIRNetworkCompletionHandler)handler {
+         completionHandler:(GULNetworkCompletionHandler)handler {
   if (!url.absoluteString.length) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkInvalidURL queue:queue withHandler:handler];
+    [self handleErrorWithCode:GULErrorCodeNetworkInvalidURL queue:queue withHandler:handler];
     return nil;
   }
 
-  NSTimeInterval timeOutInterval = _timeoutInterval ?: kFIRNetworkTimeOutInterval;
+  NSTimeInterval timeOutInterval = _timeoutInterval ?: kGULNetworkTimeOutInterval;
   NSMutableURLRequest *request =
       [[NSMutableURLRequest alloc] initWithURL:url
                                    cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                timeoutInterval:timeOutInterval];
 
   if (!request) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkSessionTaskCreation
+    [self handleErrorWithCode:GULErrorCodeNetworkSessionTaskCreation
                         queue:queue
                   withHandler:handler];
     return nil;
   }
 
-  request.HTTPMethod = kFIRNetworkGETRequestMethod;
+  request.HTTPMethod = kGULNetworkGETRequestMethod;
   request.allHTTPHeaderFields = headers;
 
-  FIRNetworkURLSession *fetcher = [[FIRNetworkURLSession alloc] initWithNetworkLoggerDelegate:self];
+  GULNetworkURLSession *fetcher = [[GULNetworkURLSession alloc] initWithNetworkLoggerDelegate:self];
   fetcher.backgroundNetworkEnabled = usingBackgroundSession;
 
-  __weak FIRNetwork *weakSelf = self;
+  __weak GULNetwork *weakSelf = self;
   NSString *requestID = [fetcher
       sessionIDFromAsyncGETRequest:request
                  completionHandler:^(NSHTTPURLResponse *response, NSData *data, NSString *sessionID,
                                      NSError *error) {
-                   FIRNetwork *strongSelf = weakSelf;
+                   GULNetwork *strongSelf = weakSelf;
                    if (!strongSelf) {
                      return;
                    }
@@ -225,14 +223,14 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
                  }];
 
   if (!requestID) {
-    [self handleErrorWithCode:FIRErrorCodeNetworkSessionTaskCreation
+    [self handleErrorWithCode:GULErrorCodeNetworkSessionTaskCreation
                         queue:queue
                   withHandler:handler];
     return nil;
   }
 
-  [self firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                    messageCode:kFIRNetworkMessageCodeNetwork001
+  [self GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                    messageCode:kGULNetworkMessageCodeNetwork001
                         message:@"Downloading data. Host"
                         context:url];
   _requests[requestID] = fetcher;
@@ -247,26 +245,26 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
 
 /// Tells reachability delegate to call reachabilityDidChangeToStatus: to notify the network
 /// reachability has changed.
-- (void)reachability:(FIRReachabilityChecker *)reachability
-       statusChanged:(FIRReachabilityStatus)status {
-  _networkConnected = (status == kFIRReachabilityViaCellular || status == kFIRReachabilityViaWifi);
+- (void)reachability:(GULReachabilityChecker *)reachability
+       statusChanged:(GULReachabilityStatus)status {
+  _networkConnected = (status == kGULReachabilityViaCellular || status == kGULReachabilityViaWifi);
   [_reachabilityDelegate reachabilityDidChange];
 }
 
 #pragma mark - Network logger delegate
 
-- (void)setLoggerDelegate:(id<FIRNetworkLoggerDelegate>)loggerDelegate {
+- (void)setLoggerDelegate:(id<GULNetworkLoggerDelegate>)loggerDelegate {
   // Explicitly check whether the delegate responds to the methods because conformsToProtocol does
   // not work correctly even though the delegate does respond to the methods.
   if (!loggerDelegate ||
       ![loggerDelegate
-          respondsToSelector:@selector(firNetwork_logWithLevel:messageCode:message:contexts:)] ||
+          respondsToSelector:@selector(GULNetwork_logWithLevel:messageCode:message:contexts:)] ||
       ![loggerDelegate
-          respondsToSelector:@selector(firNetwork_logWithLevel:messageCode:message:context:)] ||
+          respondsToSelector:@selector(GULNetwork_logWithLevel:messageCode:message:context:)] ||
       !
-      [loggerDelegate respondsToSelector:@selector(firNetwork_logWithLevel:messageCode:message:)]) {
-    FIRLogError(kFIRLoggerAnalytics,
-                [NSString stringWithFormat:@"I-NET%06ld", (long)kFIRNetworkMessageCodeNetwork002],
+      [loggerDelegate respondsToSelector:@selector(GULNetwork_logWithLevel:messageCode:message:)]) {
+    GULLogError(kGULLoggerNetwork, NO,
+                [NSString stringWithFormat:@"I-NET%06ld", (long)kGULNetworkMessageCodeNetwork002],
                 @"Cannot set the network logger delegate: delegate does not conform to the network "
                  "logger protocol.");
     return;
@@ -279,12 +277,12 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
 /// Handles network error and calls completion handler with the error.
 - (void)handleErrorWithCode:(NSInteger)code
                       queue:(dispatch_queue_t)queue
-                withHandler:(FIRNetworkCompletionHandler)handler {
-  NSDictionary *userInfo = @{kFIRNetworkErrorContext : @"Failed to create network request"};
+                withHandler:(GULNetworkCompletionHandler)handler {
+  NSDictionary *userInfo = @{kGULNetworkErrorContext : @"Failed to create network request"};
   NSError *error =
-      [[NSError alloc] initWithDomain:kFIRNetworkErrorDomain code:code userInfo:userInfo];
-  [self firNetwork_logWithLevel:kFIRNetworkLogLevelWarning
-                    messageCode:kFIRNetworkMessageCodeNetwork002
+      [[NSError alloc] initWithDomain:kGULNetworkErrorDomain code:code userInfo:userInfo];
+  [self GULNetwork_logWithLevel:kGULNetworkLogLevelWarning
+                    messageCode:kGULNetworkMessageCodeNetwork002
                         message:@"Failed to create network request. Code, error"
                        contexts:@[ @(code), error ]];
   if (handler) {
@@ -297,72 +295,72 @@ static NSString *const kFIRNetworkLogTag = @"Firebase/Network";
 
 #pragma mark - Network logger
 
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message
                        contexts:(NSArray *)contexts {
   // Let the delegate log the message if there is a valid logger delegate. Otherwise, just log
   // errors/warnings/info messages to the console log.
   if (_loggerDelegate) {
-    [_loggerDelegate firNetwork_logWithLevel:logLevel
+    [_loggerDelegate GULNetwork_logWithLevel:logLevel
                                  messageCode:messageCode
                                      message:message
                                     contexts:contexts];
     return;
   }
-  if (_isDebugModeEnabled || logLevel == kFIRNetworkLogLevelError ||
-      logLevel == kFIRNetworkLogLevelWarning || logLevel == kFIRNetworkLogLevelInfo) {
-    NSString *formattedMessage = FIRStringWithLogMessage(message, logLevel, contexts);
+  if (_isDebugModeEnabled || logLevel == kGULNetworkLogLevelError ||
+      logLevel == kGULNetworkLogLevelWarning || logLevel == kGULNetworkLogLevelInfo) {
+    NSString *formattedMessage = GULStringWithLogMessage(message, logLevel, contexts);
     NSLog(@"%@", formattedMessage);
-    FIRLogBasic((FIRLoggerLevel)logLevel, kFIRLoggerCore,
+    GULLogBasic((GULLoggerLevel)logLevel, kGULLoggerNetwork, NO,
                 [NSString stringWithFormat:@"I-NET%06ld", (long)messageCode], formattedMessage,
                 NULL);
   }
 }
 
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message
                         context:(id)context {
   if (_loggerDelegate) {
-    [_loggerDelegate firNetwork_logWithLevel:logLevel
+    [_loggerDelegate GULNetwork_logWithLevel:logLevel
                                  messageCode:messageCode
                                      message:message
                                      context:context];
     return;
   }
   NSArray *contexts = context ? @[ context ] : @[];
-  [self firNetwork_logWithLevel:logLevel messageCode:messageCode message:message contexts:contexts];
+  [self GULNetwork_logWithLevel:logLevel messageCode:messageCode message:message contexts:contexts];
 }
 
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message {
   if (_loggerDelegate) {
-    [_loggerDelegate firNetwork_logWithLevel:logLevel messageCode:messageCode message:message];
+    [_loggerDelegate GULNetwork_logWithLevel:logLevel messageCode:messageCode message:message];
     return;
   }
-  [self firNetwork_logWithLevel:logLevel messageCode:messageCode message:message contexts:@[]];
+  [self GULNetwork_logWithLevel:logLevel messageCode:messageCode message:message contexts:@[]];
 }
 
-/// Returns a string for the given log level (e.g. kFIRNetworkLogLevelError -> @"ERROR").
-static NSString *FIRLogLevelDescriptionFromLogLevel(FIRNetworkLogLevel logLevel) {
+/// Returns a string for the given log level (e.g. kGULNetworkLogLevelError -> @"ERROR").
+static NSString *GULLogLevelDescriptionFromLogLevel(GULNetworkLogLevel logLevel) {
   static NSDictionary *levelNames = nil;
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
     levelNames = @{
-      @(kFIRNetworkLogLevelError) : @"ERROR",
-      @(kFIRNetworkLogLevelWarning) : @"WARNING",
-      @(kFIRNetworkLogLevelInfo) : @"INFO",
-      @(kFIRNetworkLogLevelDebug) : @"DEBUG"
+      @(kGULNetworkLogLevelError) : @"ERROR",
+      @(kGULNetworkLogLevelWarning) : @"WARNING",
+      @(kGULNetworkLogLevelInfo) : @"INFO",
+      @(kGULNetworkLogLevelDebug) : @"DEBUG"
     };
   });
   return levelNames[@(logLevel)];
 }
 
 /// Returns a formatted string to be used for console logging.
-static NSString *FIRStringWithLogMessage(NSString *message,
-                                         FIRNetworkLogLevel logLevel,
+static NSString *GULStringWithLogMessage(NSString *message,
+                                         GULNetworkLogLevel logLevel,
                                          NSArray *contexts) {
   if (!message) {
     message = @"(Message was nil)";
@@ -370,7 +368,7 @@ static NSString *FIRStringWithLogMessage(NSString *message,
     message = @"(Message was empty)";
   }
   NSMutableString *result = [[NSMutableString alloc]
-      initWithFormat:@"<%@/%@> %@", kFIRNetworkLogTag, FIRLogLevelDescriptionFromLogLevel(logLevel),
+      initWithFormat:@"<%@/%@> %@", kGULNetworkLogTag, GULLogLevelDescriptionFromLogLevel(logLevel),
                      message];
 
   if (!contexts.count) {
diff --git a/Firebase/Utilities/Network/GULNetworkConstants.m b/Firebase/Utilities/Network/GULNetworkConstants.m
new file mode 100644
index 0000000..90bd03d
--- /dev/null
+++ b/Firebase/Utilities/Network/GULNetworkConstants.m
@@ -0,0 +1,40 @@
+// Copyright 2017 Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "Private/GULNetworkConstants.h"
+
+#import <Foundation/Foundation.h>
+
+NSString *const kGULNetworkBackgroundSessionConfigIDPrefix = @"com.gul.network.background-upload";
+NSString *const kGULNetworkApplicationSupportSubdirectory = @"GUL/Network";
+NSString *const kGULNetworkTempDirectoryName = @"GULNetworkTemporaryDirectory";
+const NSTimeInterval kGULNetworkTempFolderExpireTime = 60 * 60;  // 1 hour
+const NSTimeInterval kGULNetworkTimeOutInterval = 60;            // 1 minute.
+NSString *const kGULNetworkReachabilityHost = @"app-measurement.com";
+NSString *const kGULNetworkErrorContext = @"Context";
+
+const int kGULNetworkHTTPStatusOK = 200;
+const int kGULNetworkHTTPStatusNoContent = 204;
+const int kGULNetworkHTTPStatusCodeMultipleChoices = 300;
+const int kGULNetworkHTTPStatusCodeMovedPermanently = 301;
+const int kGULNetworkHTTPStatusCodeFound = 302;
+const int kGULNetworkHTTPStatusCodeNotModified = 304;
+const int kGULNetworkHTTPStatusCodeMovedTemporarily = 307;
+const int kGULNetworkHTTPStatusCodeNotFound = 404;
+const int kGULNetworkHTTPStatusCodeCannotAcceptTraffic = 429;
+const int kGULNetworkHTTPStatusCodeUnavailable = 503;
+
+NSString *const kGULNetworkErrorDomain = @"com.gul.network.ErrorDomain";
+
+GULLoggerService kGULLoggerNetwork = @"[GULNetwork]";
diff --git a/Firebase/Core/FIRNetworkURLSession.m b/Firebase/Utilities/Network/GULNetworkURLSession.m
index 470d3e9..cb8a204 100644
--- a/Firebase/Core/FIRNetworkURLSession.m
+++ b/Firebase/Utilities/Network/GULNetworkURLSession.m
@@ -14,16 +14,16 @@
 
 #import <Foundation/Foundation.h>
 
-#import "Private/FIRNetworkURLSession.h"
+#import "Private/GULNetworkURLSession.h"
 
-#import "Private/FIRLogger.h"
-#import "Private/FIRMutableDictionary.h"
-#import "Private/FIRNetworkConstants.h"
-#import "Private/FIRNetworkMessageCode.h"
+#import <GoogleUtilities/GULLogger.h>
+#import "Private/GULMutableDictionary.h"
+#import "Private/GULNetworkConstants.h"
+#import "Private/GULNetworkMessageCode.h"
 
-@implementation FIRNetworkURLSession {
+@implementation GULNetworkURLSession {
   /// The handler to be called when the request completes or error has occurs.
-  FIRNetworkURLSessionCompletionHandler _completionHandler;
+  GULNetworkURLSessionCompletionHandler _completionHandler;
 
   /// Session ID generated randomly with a fixed prefix.
   NSString *_sessionID;
@@ -46,7 +46,7 @@
 
 #pragma mark - Init
 
-- (instancetype)initWithNetworkLoggerDelegate:(id<FIRNetworkLoggerDelegate>)networkLoggerDelegate {
+- (instancetype)initWithNetworkLoggerDelegate:(id<GULNetworkLoggerDelegate>)networkLoggerDelegate {
   self = [super init];
   if (self) {
     // Create URL to the directory where all temporary files to upload have to be stored.
@@ -54,11 +54,11 @@
         NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
     NSString *applicationSupportDirectory = paths.firstObject;
     NSArray *tempPathComponents = @[
-      applicationSupportDirectory, kFIRNetworkApplicationSupportSubdirectory,
-      kFIRNetworkTempDirectoryName
+      applicationSupportDirectory, kGULNetworkApplicationSupportSubdirectory,
+      kGULNetworkTempDirectoryName
     ];
     _networkDirectoryURL = [NSURL fileURLWithPathComponents:tempPathComponents];
-    _sessionID = [NSString stringWithFormat:@"%@-%@", kFIRNetworkBackgroundSessionConfigIDPrefix,
+    _sessionID = [NSString stringWithFormat:@"%@-%@", kGULNetworkBackgroundSessionConfigIDPrefix,
                                             [[NSUUID UUID] UUIDString]];
     _loggerDelegate = networkLoggerDelegate;
   }
@@ -71,17 +71,17 @@
 
 + (void)handleEventsForBackgroundURLSessionID:(NSString *)sessionID
                             completionHandler:
-                                (FIRNetworkSystemCompletionHandler)systemCompletionHandler {
-  // The session may not be FIRAnalytics background. Ignore those that do not have the prefix.
-  if (![sessionID hasPrefix:kFIRNetworkBackgroundSessionConfigIDPrefix]) {
+                                (GULNetworkSystemCompletionHandler)systemCompletionHandler {
+  // The session may not be Analytics background. Ignore those that do not have the prefix.
+  if (![sessionID hasPrefix:kGULNetworkBackgroundSessionConfigIDPrefix]) {
     return;
   }
-  FIRNetworkURLSession *fetcher = [self fetcherWithSessionIdentifier:sessionID];
+  GULNetworkURLSession *fetcher = [self fetcherWithSessionIdentifier:sessionID];
   if (fetcher != nil) {
     [fetcher addSystemCompletionHandler:systemCompletionHandler forSession:sessionID];
   } else {
-    FIRLogError(kFIRLoggerCore,
-                [NSString stringWithFormat:@"I-NET%06ld", (long)kFIRNetworkMessageCodeNetwork003],
+    GULLogError(kGULLoggerNetwork, NO,
+                [NSString stringWithFormat:@"I-NET%06ld", (long)kGULNetworkMessageCodeNetwork003],
                 @"Failed to retrieve background session with ID %@ after app is relaunched.",
                 sessionID);
   }
@@ -92,7 +92,7 @@
 /// Sends an async POST request using NSURLSession for iOS >= 7.0, and returns an ID of the
 /// connection.
 - (NSString *)sessionIDFromAsyncPOSTRequest:(NSURLRequest *)request
-                          completionHandler:(FIRNetworkURLSessionCompletionHandler)handler {
+                          completionHandler:(GULNetworkURLSessionCompletionHandler)handler {
   // NSURLSessionUploadTask does not work with NSData in the background.
   // To avoid this issue, write the data to a temporary file to upload it.
   // Make a temporary file with the data subset.
@@ -105,7 +105,7 @@
   // Clean up the entire temp folder to avoid temp files that remain in case the previous session
   // crashed and did not clean up.
   [self maybeRemoveTempFilesAtURL:_networkDirectoryURL
-                     expiringTime:kFIRNetworkTempFolderExpireTime];
+                     expiringTime:kGULNetworkTempFolderExpireTime];
 
   // If there is no background network enabled, no need to write to file. This will allow default
   // network session which runs on the foreground.
@@ -115,8 +115,8 @@
                                            error:&writeError];
 
     if (writeError) {
-      [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                   messageCode:kFIRNetworkMessageCodeURLSession000
+      [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                   messageCode:kGULNetworkMessageCodeURLSession000
                                        message:@"Failed to write request data to file"
                                        context:writeError];
     }
@@ -146,9 +146,9 @@
 
   if (!session || !postRequestTask) {
     NSError *error = [[NSError alloc]
-        initWithDomain:kFIRNetworkErrorDomain
-                  code:FIRErrorCodeNetworkRequestCreation
-              userInfo:@{kFIRNetworkErrorContext : @"Cannot create network session"}];
+        initWithDomain:kGULNetworkErrorDomain
+                  code:GULErrorCodeNetworkRequestCreation
+              userInfo:@{kGULNetworkErrorContext : @"Cannot create network session"}];
     [self callCompletionHandler:handler withResponse:nil data:nil error:error];
     return nil;
   }
@@ -169,7 +169,7 @@
 
 /// Sends an async GET request using NSURLSession for iOS >= 7.0, and returns an ID of the session.
 - (NSString *)sessionIDFromAsyncGETRequest:(NSURLRequest *)request
-                         completionHandler:(FIRNetworkURLSessionCompletionHandler)handler {
+                         completionHandler:(GULNetworkURLSessionCompletionHandler)handler {
   if (_backgroundNetworkEnabled) {
     _sessionConfig = [self backgroundSessionConfigWithSessionID:_sessionID];
   } else {
@@ -188,9 +188,9 @@
 
   if (!session || !downloadTask) {
     NSError *error = [[NSError alloc]
-        initWithDomain:kFIRNetworkErrorDomain
-                  code:FIRErrorCodeNetworkRequestCreation
-              userInfo:@{kFIRNetworkErrorContext : @"Cannot create network session"}];
+        initWithDomain:kGULNetworkErrorDomain
+                  code:GULErrorCodeNetworkRequestCreation
+              userInfo:@{kGULNetworkErrorContext : @"Cannot create network session"}];
     [self callCompletionHandler:handler withResponse:nil data:nil error:error];
     return nil;
   }
@@ -218,8 +218,8 @@
     didFinishDownloadingToURL:(NSURL *)url {
   if (!url.path) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                    messageCode:kFIRNetworkMessageCodeURLSession001
+        GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                    messageCode:kGULNetworkMessageCodeURLSession001
                         message:@"Unable to read downloaded data from empty temp path"];
     _downloadedData = nil;
     return;
@@ -229,8 +229,8 @@
   _downloadedData = [NSData dataWithContentsOfFile:url.path options:0 error:&error];
 
   if (error) {
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeURLSession002
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                 messageCode:kGULNetworkMessageCodeURLSession002
                                      message:@"Cannot read the content of downloaded data"
                                      context:error];
     _downloadedData = nil;
@@ -239,8 +239,8 @@
 
 #if TARGET_OS_IOS || TARGET_OS_TV
 - (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session {
-  [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                               messageCode:kFIRNetworkMessageCodeURLSession003
+  [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                               messageCode:kGULNetworkMessageCodeURLSession003
                                    message:@"Background session finished"
                                    context:session.configuration.identifier];
   [self callSystemCompletionHandler:session.configuration.identifier];
@@ -251,7 +251,7 @@
                     task:(NSURLSessionTask *)task
     didCompleteWithError:(NSError *)error {
   // Avoid any chance of recursive behavior leading to it being used repeatedly.
-  FIRNetworkURLSessionCompletionHandler handler = _completionHandler;
+  GULNetworkURLSessionCompletionHandler handler = _completionHandler;
   _completionHandler = nil;
 
   if (task.response) {
@@ -262,9 +262,9 @@
     error = nil;
   } else if (!error) {
     error = [[NSError alloc]
-        initWithDomain:kFIRNetworkErrorDomain
-                  code:FIRErrorCodeNetworkInvalidResponse
-              userInfo:@{kFIRNetworkErrorContext : @"Network Error: Empty network response"}];
+        initWithDomain:kGULNetworkErrorDomain
+                  code:GULErrorCodeNetworkInvalidResponse
+              userInfo:@{kGULNetworkErrorContext : @"Network Error: Empty network response"}];
   }
 
   [self callCompletionHandler:handler
@@ -277,7 +277,7 @@
 
   // Try to clean up stale files again.
   [self maybeRemoveTempFilesAtURL:_networkDirectoryURL
-                     expiringTime:kFIRNetworkTempFolderExpireTime];
+                     expiringTime:kGULNetworkTempFolderExpireTime];
 }
 
 - (void)URLSession:(NSURLSession *)session
@@ -290,8 +290,8 @@
           isEqualToString:NSURLAuthenticationMethodServerTrust]) {
     SecTrustRef serverTrust = challenge.protectionSpace.serverTrust;
     if (serverTrust == NULL) {
-      [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                                   messageCode:kFIRNetworkMessageCodeURLSession004
+      [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                                   messageCode:kGULNetworkMessageCodeURLSession004
                                        message:@"Received empty server trust for host. Host"
                                        context:_request.URL];
       completionHandler(NSURLSessionAuthChallengePerformDefaultHandling, nil);
@@ -299,16 +299,16 @@
     }
     NSURLCredential *credential = [NSURLCredential credentialForTrust:serverTrust];
     if (!credential) {
-      [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelWarning
-                                   messageCode:kFIRNetworkMessageCodeURLSession005
+      [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelWarning
+                                   messageCode:kGULNetworkMessageCodeURLSession005
                                        message:@"Unable to verify server identity. Host"
                                        context:_request.URL];
       completionHandler(NSURLSessionAuthChallengeCancelAuthenticationChallenge, nil);
       return;
     }
 
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                                 messageCode:kFIRNetworkMessageCodeURLSession006
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                                 messageCode:kGULNetworkMessageCodeURLSession006
                                      message:@"Received SSL challenge for host. Host"
                                      context:_request.URL];
 
@@ -317,8 +317,8 @@
         completionHandler(NSURLSessionAuthChallengeUseCredential, credential);
       } else {
         [self->_loggerDelegate
-            firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                        messageCode:kFIRNetworkMessageCodeURLSession007
+            GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                        messageCode:kGULNetworkMessageCodeURLSession007
                             message:@"Cancelling authentication challenge for host. Host"
                             context:self->_request.URL];
         completionHandler(NSURLSessionAuthChallengeCancelAuthenticationChallenge, nil);
@@ -341,13 +341,13 @@
       BOOL shouldAllow;
       OSStatus trustError;
 
-      @synchronized([FIRNetworkURLSession class]) {
+      @synchronized([GULNetworkURLSession class]) {
         trustError = SecTrustEvaluate(serverTrust, &trustEval);
       }
 
       if (trustError != errSecSuccess) {
-        [self->_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                           messageCode:kFIRNetworkMessageCodeURLSession008
+        [self->_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                           messageCode:kGULNetworkMessageCodeURLSession008
                                                message:@"Cannot evaluate server trust. Error, host"
                                               contexts:@[ @(trustError), self->_request.URL ]];
         shouldAllow = NO;
@@ -373,31 +373,31 @@
 #pragma mark - Internal Methods
 
 /// Stores system completion handler with session ID as key.
-- (void)addSystemCompletionHandler:(FIRNetworkSystemCompletionHandler)handler
+- (void)addSystemCompletionHandler:(GULNetworkSystemCompletionHandler)handler
                         forSession:(NSString *)identifier {
   if (!handler) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                    messageCode:kFIRNetworkMessageCodeURLSession009
+        GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                    messageCode:kGULNetworkMessageCodeURLSession009
                         message:@"Cannot store nil system completion handler in network"];
     return;
   }
 
   if (!identifier.length) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                    messageCode:kFIRNetworkMessageCodeURLSession010
+        GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                    messageCode:kGULNetworkMessageCodeURLSession010
                         message:
                             @"Cannot store system completion handler with empty network "
                              "session identifier"];
     return;
   }
 
-  FIRMutableDictionary *systemCompletionHandlers =
+  GULMutableDictionary *systemCompletionHandlers =
       [[self class] sessionIDToSystemCompletionHandlerDictionary];
   if (systemCompletionHandlers[identifier]) {
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelWarning
-                                 messageCode:kFIRNetworkMessageCodeURLSession011
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelWarning
+                                 messageCode:kGULNetworkMessageCodeURLSession011
                                      message:@"Got multiple system handlers for a single session ID"
                                      context:identifier];
   }
@@ -408,9 +408,9 @@
 /// Calls the system provided completion handler with the session ID stored in the dictionary.
 /// The handler will be removed from the dictionary after being called.
 - (void)callSystemCompletionHandler:(NSString *)identifier {
-  FIRMutableDictionary *systemCompletionHandlers =
+  GULMutableDictionary *systemCompletionHandlers =
       [[self class] sessionIDToSystemCompletionHandlerDictionary];
-  FIRNetworkSystemCompletionHandler handler = [systemCompletionHandlers objectForKey:identifier];
+  GULNetworkSystemCompletionHandler handler = [systemCompletionHandlers objectForKey:identifier];
 
   if (handler) {
     [systemCompletionHandlers removeObjectForKey:identifier];
@@ -473,8 +473,8 @@
                                       error:&error];
   if (error && error.code != NSFileReadNoSuchFileError) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                    messageCode:kFIRNetworkMessageCodeURLSession012
+        GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
+                    messageCode:kGULNetworkMessageCodeURLSession012
                         message:@"Cannot get files from the temporary network folder. Error"
                         context:error];
     return;
@@ -511,8 +511,8 @@
 
   if (![fileManager removeItemAtURL:fileURL error:&error] && error.code != NSFileNoSuchFileError) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                    messageCode:kFIRNetworkMessageCodeURLSession013
+        GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                    messageCode:kGULNetworkMessageCodeURLSession013
                         message:@"Failed to remove temporary uploading data file. Error"
                         context:error.localizedDescription];
   }
@@ -521,9 +521,9 @@
 /// Gets the fetcher with the session ID.
 + (instancetype)fetcherWithSessionIdentifier:(NSString *)sessionIdentifier {
   NSMapTable *sessionIdentifierToFetcherMap = [self sessionIDToFetcherMap];
-  FIRNetworkURLSession *session = [sessionIdentifierToFetcherMap objectForKey:sessionIdentifier];
-  if (!session && [sessionIdentifier hasPrefix:kFIRNetworkBackgroundSessionConfigIDPrefix]) {
-    session = [[FIRNetworkURLSession alloc] initWithNetworkLoggerDelegate:nil];
+  GULNetworkURLSession *session = [sessionIdentifierToFetcherMap objectForKey:sessionIdentifier];
+  if (!session && [sessionIdentifier hasPrefix:kGULNetworkBackgroundSessionConfigIDPrefix]) {
+    session = [[GULNetworkURLSession alloc] initWithNetworkLoggerDelegate:nil];
     [session setSessionID:sessionIdentifier];
     [sessionIdentifierToFetcherMap setObject:session forKey:sessionIdentifier];
   }
@@ -543,18 +543,18 @@
 
 /// Returns a map of system provided completion handler by session ID. Creates a map if it is not
 /// created.
-+ (FIRMutableDictionary *)sessionIDToSystemCompletionHandlerDictionary {
-  static FIRMutableDictionary *systemCompletionHandlers;
++ (GULMutableDictionary *)sessionIDToSystemCompletionHandlerDictionary {
+  static GULMutableDictionary *systemCompletionHandlers;
 
   static dispatch_once_t systemCompletionHandlerOnceToken;
   dispatch_once(&systemCompletionHandlerOnceToken, ^{
-    systemCompletionHandlers = [[FIRMutableDictionary alloc] init];
+    systemCompletionHandlers = [[GULMutableDictionary alloc] init];
   });
   return systemCompletionHandlers;
 }
 
 - (NSURL *)temporaryFilePathWithSessionID:(NSString *)sessionID {
-  NSString *tempName = [NSString stringWithFormat:@"FIRUpload_temp_%@", sessionID];
+  NSString *tempName = [NSString stringWithFormat:@"GULUpload_temp_%@", sessionID];
   return [_networkDirectoryURL URLByAppendingPathComponent:tempName];
 }
 
@@ -571,8 +571,8 @@
 
   if (error && error.code != NSFileReadNoSuchFileError) {
     [_loggerDelegate
-        firNetwork_logWithLevel:kFIRNetworkLogLevelWarning
-                    messageCode:kFIRNetworkMessageCodeURLSession014
+        GULNetwork_logWithLevel:kGULNetworkLogLevelWarning
+                    messageCode:kGULNetworkMessageCodeURLSession014
                         message:@"Error while trying to access Network temp folder. Error"
                         context:error];
   }
@@ -584,8 +584,8 @@
                          attributes:nil
                               error:&writeError];
   if (writeError) {
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeURLSession015
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                 messageCode:kGULNetworkMessageCodeURLSession015
                                      message:@"Cannot create temporary directory. Error"
                                      context:writeError];
     return NO;
@@ -606,8 +606,8 @@
   NSError *preventBackupError = nil;
   [url setResourceValue:@YES forKey:NSURLIsExcludedFromBackupKey error:&preventBackupError];
   if (preventBackupError) {
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeURLSession016
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                 messageCode:kGULNetworkMessageCodeURLSession016
                                      message:@"Cannot exclude temporary folder from iTunes backup"];
   }
 }
@@ -618,8 +618,8 @@
                     newRequest:(NSURLRequest *)request
              completionHandler:(void (^)(NSURLRequest *))completionHandler {
   NSArray *nonAllowedRedirectionCodes = @[
-    @(kFIRNetworkHTTPStatusCodeFound), @(kFIRNetworkHTTPStatusCodeMovedPermanently),
-    @(kFIRNetworkHTTPStatusCodeMovedTemporarily), @(kFIRNetworkHTTPStatusCodeMultipleChoices)
+    @(kGULNetworkHTTPStatusCodeFound), @(kGULNetworkHTTPStatusCodeMovedPermanently),
+    @(kGULNetworkHTTPStatusCodeMovedTemporarily), @(kGULNetworkHTTPStatusCodeMultipleChoices)
   ];
 
   // Allow those not in the non allowed list to be followed.
@@ -640,13 +640,13 @@
 
 #pragma mark - Helper Methods
 
-- (void)callCompletionHandler:(FIRNetworkURLSessionCompletionHandler)handler
+- (void)callCompletionHandler:(GULNetworkURLSessionCompletionHandler)handler
                  withResponse:(NSHTTPURLResponse *)response
                          data:(NSData *)data
                         error:(NSError *)error {
   if (error) {
-    [_loggerDelegate firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeURLSession017
+    [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelError
+                                 messageCode:kGULNetworkMessageCodeURLSession017
                                      message:@"Encounter network error. Code, error"
                                     contexts:@[ @(error.code), error ]];
   }
diff --git a/Firebase/Core/Private/FIRMutableDictionary.h b/Firebase/Utilities/Network/Private/GULMutableDictionary.h
index 6829dbc..a8cc45b 100644
--- a/Firebase/Core/Private/FIRMutableDictionary.h
+++ b/Firebase/Utilities/Network/Private/GULMutableDictionary.h
@@ -17,7 +17,7 @@
 #import <Foundation/Foundation.h>
 
 /// A mutable dictionary that provides atomic accessor and mutators.
-@interface FIRMutableDictionary : NSObject
+@interface GULMutableDictionary : NSObject
 
 /// Returns an object given a key in the dictionary or nil if not found.
 - (id)objectForKey:(id)key;
diff --git a/Firebase/Core/Private/FIRNetwork.h b/Firebase/Utilities/Network/Private/GULNetwork.h
index 32be35a..0e75ae5 100644
--- a/Firebase/Core/Private/FIRNetwork.h
+++ b/Firebase/Utilities/Network/Private/GULNetwork.h
@@ -16,12 +16,12 @@
 
 #import <Foundation/Foundation.h>
 
-#import "FIRNetworkConstants.h"
-#import "FIRNetworkLoggerProtocol.h"
-#import "FIRNetworkURLSession.h"
+#import "GULNetworkConstants.h"
+#import "GULNetworkLoggerProtocol.h"
+#import "GULNetworkURLSession.h"
 
-/// Delegate protocol for FIRNetwork events.
-@protocol FIRNetworkReachabilityDelegate
+/// Delegate protocol for GULNetwork events.
+@protocol GULNetworkReachabilityDelegate
 
 /// Tells the delegate to handle events when the network reachability changes to connected or not
 /// connected.
@@ -35,7 +35,7 @@
 /// NOTE:
 /// User must add FIRAnalytics handleEventsForBackgroundURLSessionID:completionHandler to the
 /// AppDelegate application:handleEventsForBackgroundURLSession:completionHandler:
-@interface FIRNetwork : NSObject
+@interface GULNetwork : NSObject
 
 /// Indicates if network connectivity is available.
 @property(nonatomic, readonly, getter=isNetworkConnected) BOOL networkConnected;
@@ -44,11 +44,11 @@
 @property(nonatomic, readonly, getter=hasUploadInProgress) BOOL uploadInProgress;
 
 /// An optional delegate that can be used in the event when network reachability changes.
-@property(nonatomic, weak) id<FIRNetworkReachabilityDelegate> reachabilityDelegate;
+@property(nonatomic, weak) id<GULNetworkReachabilityDelegate> reachabilityDelegate;
 
 /// An optional delegate that can be used to log messages, warnings or errors that occur in the
 /// network operations.
-@property(nonatomic, weak) id<FIRNetworkLoggerDelegate> loggerDelegate;
+@property(nonatomic, weak) id<GULNetworkLoggerDelegate> loggerDelegate;
 
 /// Indicates whether the logger should display debug messages.
 @property(nonatomic, assign) BOOL isDebugModeEnabled;
@@ -64,7 +64,7 @@
 
 /// Handles events when background session with the given ID has finished.
 + (void)handleEventsForBackgroundURLSessionID:(NSString *)sessionID
-                            completionHandler:(FIRNetworkSystemCompletionHandler)completionHandler;
+                            completionHandler:(GULNetworkSystemCompletionHandler)completionHandler;
 
 /// Compresses and sends a POST request with the provided data to the URL. The session will be
 /// background session if usingBackgroundSession is YES. Otherwise, the POST session is default
@@ -73,7 +73,7 @@
                    payload:(NSData *)payload
                      queue:(dispatch_queue_t)queue
     usingBackgroundSession:(BOOL)usingBackgroundSession
-         completionHandler:(FIRNetworkCompletionHandler)handler;
+         completionHandler:(GULNetworkCompletionHandler)handler;
 
 /// Sends a GET request with the provided data to the URL. The session will be background session
 /// if usingBackgroundSession is YES. Otherwise, the GET session is default session. Returns a
@@ -82,6 +82,6 @@
                    headers:(NSDictionary *)headers
                      queue:(dispatch_queue_t)queue
     usingBackgroundSession:(BOOL)usingBackgroundSession
-         completionHandler:(FIRNetworkCompletionHandler)handler;
+         completionHandler:(GULNetworkCompletionHandler)handler;
 
 @end
diff --git a/Firebase/Core/Private/FIRNetworkConstants.h b/Firebase/Utilities/Network/Private/GULNetworkConstants.h
index d318581..44d440b 100644
--- a/Firebase/Core/Private/FIRNetworkConstants.h
+++ b/Firebase/Utilities/Network/Private/GULNetworkConstants.h
@@ -15,61 +15,65 @@
  */
 
 #import <Foundation/Foundation.h>
+#import <GoogleUtilities/GULLogger.h>
 
 /// Error codes in Firebase Network error domain.
 /// Note: these error codes should never change. It would make it harder to decode the errors if
 /// we inadvertently altered any of these codes in a future SDK version.
-typedef NS_ENUM(NSInteger, FIRNetworkErrorCode) {
+typedef NS_ENUM(NSInteger, GULNetworkErrorCode) {
   /// Unknown error.
-  FIRNetworkErrorCodeUnknown = 0,
+  GULNetworkErrorCodeUnknown = 0,
   /// Error occurs when the request URL is invalid.
-  FIRErrorCodeNetworkInvalidURL = 1,
+  GULErrorCodeNetworkInvalidURL = 1,
   /// Error occurs when request cannot be constructed.
-  FIRErrorCodeNetworkRequestCreation = 2,
+  GULErrorCodeNetworkRequestCreation = 2,
   /// Error occurs when payload cannot be compressed.
-  FIRErrorCodeNetworkPayloadCompression = 3,
+  GULErrorCodeNetworkPayloadCompression = 3,
   /// Error occurs when session task cannot be created.
-  FIRErrorCodeNetworkSessionTaskCreation = 4,
+  GULErrorCodeNetworkSessionTaskCreation = 4,
   /// Error occurs when there is no response.
-  FIRErrorCodeNetworkInvalidResponse = 5
+  GULErrorCodeNetworkInvalidResponse = 5
 };
 
 #pragma mark - Network constants
 
 /// The prefix of the ID of the background session.
-extern NSString *const kFIRNetworkBackgroundSessionConfigIDPrefix;
+extern NSString *const kGULNetworkBackgroundSessionConfigIDPrefix;
 
 /// The sub directory to store the files of data that is being uploaded in the background.
-extern NSString *const kFIRNetworkApplicationSupportSubdirectory;
+extern NSString *const kGULNetworkApplicationSupportSubdirectory;
 
 /// Name of the temporary directory that stores files for background uploading.
-extern NSString *const kFIRNetworkTempDirectoryName;
+extern NSString *const kGULNetworkTempDirectoryName;
 
 /// The period when the temporary uploading file can stay.
-extern const NSTimeInterval kFIRNetworkTempFolderExpireTime;
+extern const NSTimeInterval kGULNetworkTempFolderExpireTime;
 
 /// The default network request timeout interval.
-extern const NSTimeInterval kFIRNetworkTimeOutInterval;
+extern const NSTimeInterval kGULNetworkTimeOutInterval;
 
 /// The host to check the reachability of the network.
-extern NSString *const kFIRNetworkReachabilityHost;
+extern NSString *const kGULNetworkReachabilityHost;
 
 /// The key to get the error context of the UserInfo.
-extern NSString *const kFIRNetworkErrorContext;
+extern NSString *const kGULNetworkErrorContext;
 
 #pragma mark - Network Status Code
 
-extern const int kFIRNetworkHTTPStatusOK;
-extern const int kFIRNetworkHTTPStatusNoContent;
-extern const int kFIRNetworkHTTPStatusCodeMultipleChoices;
-extern const int kFIRNetworkHTTPStatusCodeMovedPermanently;
-extern const int kFIRNetworkHTTPStatusCodeFound;
-extern const int kFIRNetworkHTTPStatusCodeNotModified;
-extern const int kFIRNetworkHTTPStatusCodeMovedTemporarily;
-extern const int kFIRNetworkHTTPStatusCodeNotFound;
-extern const int kFIRNetworkHTTPStatusCodeCannotAcceptTraffic;
-extern const int kFIRNetworkHTTPStatusCodeUnavailable;
+extern const int kGULNetworkHTTPStatusOK;
+extern const int kGULNetworkHTTPStatusNoContent;
+extern const int kGULNetworkHTTPStatusCodeMultipleChoices;
+extern const int kGULNetworkHTTPStatusCodeMovedPermanently;
+extern const int kGULNetworkHTTPStatusCodeFound;
+extern const int kGULNetworkHTTPStatusCodeNotModified;
+extern const int kGULNetworkHTTPStatusCodeMovedTemporarily;
+extern const int kGULNetworkHTTPStatusCodeNotFound;
+extern const int kGULNetworkHTTPStatusCodeCannotAcceptTraffic;
+extern const int kGULNetworkHTTPStatusCodeUnavailable;
 
 #pragma mark - Error Domain
 
-extern NSString *const kFIRNetworkErrorDomain;
+extern NSString *const kGULNetworkErrorDomain;
+
+/// The logger service for GULNetwork.
+extern GULLoggerService kGULLoggerNetwork;
diff --git a/Firebase/Core/Private/FIRNetworkLoggerProtocol.h b/Firebase/Utilities/Network/Private/GULNetworkLoggerProtocol.h
index add70fc..f1be590 100644
--- a/Firebase/Core/Private/FIRNetworkLoggerProtocol.h
+++ b/Firebase/Utilities/Network/Private/GULNetworkLoggerProtocol.h
@@ -16,35 +16,36 @@
 
 #import <Foundation/Foundation.h>
 
-#import "FIRLoggerLevel.h"
-#import "FIRNetworkMessageCode.h"
-
-/// The log levels used by FIRNetworkLogger.
-typedef NS_ENUM(NSInteger, FIRNetworkLogLevel) {
-  kFIRNetworkLogLevelError = FIRLoggerLevelError,
-  kFIRNetworkLogLevelWarning = FIRLoggerLevelWarning,
-  kFIRNetworkLogLevelInfo = FIRLoggerLevelInfo,
-  kFIRNetworkLogLevelDebug = FIRLoggerLevelDebug,
+#import <GoogleUtilities/GULLoggerLevel.h>
+
+#import "GULNetworkMessageCode.h"
+
+/// The log levels used by GULNetworkLogger.
+typedef NS_ENUM(NSInteger, GULNetworkLogLevel) {
+  kGULNetworkLogLevelError = GULLoggerLevelError,
+  kGULNetworkLogLevelWarning = GULLoggerLevelWarning,
+  kGULNetworkLogLevelInfo = GULLoggerLevelInfo,
+  kGULNetworkLogLevelDebug = GULLoggerLevelDebug,
 };
 
-@protocol FIRNetworkLoggerDelegate <NSObject>
+@protocol GULNetworkLoggerDelegate <NSObject>
 
 @required
 /// Tells the delegate to log a message with an array of contexts and the log level.
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message
                        contexts:(NSArray *)contexts;
 
 /// Tells the delegate to log a message with a context and the log level.
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message
                         context:(id)context;
 
 /// Tells the delegate to log a message with the log level.
-- (void)firNetwork_logWithLevel:(FIRNetworkLogLevel)logLevel
-                    messageCode:(FIRNetworkMessageCode)messageCode
+- (void)GULNetwork_logWithLevel:(GULNetworkLogLevel)logLevel
+                    messageCode:(GULNetworkMessageCode)messageCode
                         message:(NSString *)message;
 
 @end
diff --git a/Firebase/Utilities/Network/Private/GULNetworkMessageCode.h b/Firebase/Utilities/Network/Private/GULNetworkMessageCode.h
new file mode 100644
index 0000000..ce78e60
--- /dev/null
+++ b/Firebase/Utilities/Network/Private/GULNetworkMessageCode.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Make sure these codes do not overlap with any contained in the FIRAMessageCode enum.
+typedef NS_ENUM(NSInteger, GULNetworkMessageCode) {
+  // GULNetwork.m
+  kGULNetworkMessageCodeNetwork000 = 900000,  // I-NET900000
+  kGULNetworkMessageCodeNetwork001 = 900001,  // I-NET900001
+  kGULNetworkMessageCodeNetwork002 = 900002,  // I-NET900002
+  kGULNetworkMessageCodeNetwork003 = 900003,  // I-NET900003
+  // GULNetworkURLSession.m
+  kGULNetworkMessageCodeURLSession000 = 901000,  // I-NET901000
+  kGULNetworkMessageCodeURLSession001 = 901001,  // I-NET901001
+  kGULNetworkMessageCodeURLSession002 = 901002,  // I-NET901002
+  kGULNetworkMessageCodeURLSession003 = 901003,  // I-NET901003
+  kGULNetworkMessageCodeURLSession004 = 901004,  // I-NET901004
+  kGULNetworkMessageCodeURLSession005 = 901005,  // I-NET901005
+  kGULNetworkMessageCodeURLSession006 = 901006,  // I-NET901006
+  kGULNetworkMessageCodeURLSession007 = 901007,  // I-NET901007
+  kGULNetworkMessageCodeURLSession008 = 901008,  // I-NET901008
+  kGULNetworkMessageCodeURLSession009 = 901009,  // I-NET901009
+  kGULNetworkMessageCodeURLSession010 = 901010,  // I-NET901010
+  kGULNetworkMessageCodeURLSession011 = 901011,  // I-NET901011
+  kGULNetworkMessageCodeURLSession012 = 901012,  // I-NET901012
+  kGULNetworkMessageCodeURLSession013 = 901013,  // I-NET901013
+  kGULNetworkMessageCodeURLSession014 = 901014,  // I-NET901014
+  kGULNetworkMessageCodeURLSession015 = 901015,  // I-NET901015
+  kGULNetworkMessageCodeURLSession016 = 901016,  // I-NET901016
+  kGULNetworkMessageCodeURLSession017 = 901017,  // I-NET901017
+  kGULNetworkMessageCodeURLSession018 = 901018,  // I-NET901018
+};
diff --git a/Firebase/Core/Private/FIRNetworkURLSession.h b/Firebase/Utilities/Network/Private/GULNetworkURLSession.h
index a51b8a9..81190c6 100644
--- a/Firebase/Core/Private/FIRNetworkURLSession.h
+++ b/Firebase/Utilities/Network/Private/GULNetworkURLSession.h
@@ -16,33 +16,33 @@
 
 #import <Foundation/Foundation.h>
 
-#import "FIRNetworkLoggerProtocol.h"
+#import "GULNetworkLoggerProtocol.h"
 
-typedef void (^FIRNetworkCompletionHandler)(NSHTTPURLResponse *response,
+typedef void (^GULNetworkCompletionHandler)(NSHTTPURLResponse *response,
                                             NSData *data,
                                             NSError *error);
-typedef void (^FIRNetworkURLSessionCompletionHandler)(NSHTTPURLResponse *response,
+typedef void (^GULNetworkURLSessionCompletionHandler)(NSHTTPURLResponse *response,
                                                       NSData *data,
                                                       NSString *sessionID,
                                                       NSError *error);
-typedef void (^FIRNetworkSystemCompletionHandler)(void);
+typedef void (^GULNetworkSystemCompletionHandler)(void);
 
 /// The protocol that uses NSURLSession for iOS >= 7.0 to handle requests and responses.
-@interface FIRNetworkURLSession
+@interface GULNetworkURLSession
     : NSObject <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDownloadDelegate>
 
 /// Indicates whether the background network is enabled. Default value is NO.
 @property(nonatomic, getter=isBackgroundNetworkEnabled) BOOL backgroundNetworkEnabled;
 
 /// The logger delegate to log message, errors or warnings that occur during the network operations.
-@property(nonatomic, weak) id<FIRNetworkLoggerDelegate> loggerDelegate;
+@property(nonatomic, weak) id<GULNetworkLoggerDelegate> loggerDelegate;
 
 /// Calls the system provided completion handler after the background session is finished.
 + (void)handleEventsForBackgroundURLSessionID:(NSString *)sessionID
-                            completionHandler:(FIRNetworkSystemCompletionHandler)completionHandler;
+                            completionHandler:(GULNetworkSystemCompletionHandler)completionHandler;
 
 /// Initializes with logger delegate.
-- (instancetype)initWithNetworkLoggerDelegate:(id<FIRNetworkLoggerDelegate>)networkLoggerDelegate
+- (instancetype)initWithNetworkLoggerDelegate:(id<GULNetworkLoggerDelegate>)networkLoggerDelegate
     NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -50,11 +50,11 @@ typedef void (^FIRNetworkSystemCompletionHandler)(void);
 /// Sends an asynchronous POST request and calls the provided completion handler when the request
 /// completes or when errors occur, and returns an ID of the session/connection.
 - (NSString *)sessionIDFromAsyncPOSTRequest:(NSURLRequest *)request
-                          completionHandler:(FIRNetworkURLSessionCompletionHandler)handler;
+                          completionHandler:(GULNetworkURLSessionCompletionHandler)handler;
 
 /// Sends an asynchronous GET request and calls the provided completion handler when the request
 /// completes or when errors occur, and returns an ID of the session.
 - (NSString *)sessionIDFromAsyncGETRequest:(NSURLRequest *)request
-                         completionHandler:(FIRNetworkURLSessionCompletionHandler)handler;
+                         completionHandler:(GULNetworkURLSessionCompletionHandler)handler;
 
 @end
diff --git a/Firebase/Core/Private/FIRReachabilityChecker+Internal.h b/Firebase/Utilities/Reachability/GULReachabilityChecker+Internal.h
index f82d103..8883c4d 100644
--- a/Firebase/Core/Private/FIRReachabilityChecker+Internal.h
+++ b/Firebase/Utilities/Reachability/GULReachabilityChecker+Internal.h
@@ -14,34 +14,34 @@
  * limitations under the License.
  */
 
-#import "FIRReachabilityChecker.h"
+#import <GoogleUtilities/GULReachabilityChecker.h>
 
-typedef SCNetworkReachabilityRef (*FIRReachabilityCreateWithNameFn)(CFAllocatorRef allocator,
+typedef SCNetworkReachabilityRef (*GULReachabilityCreateWithNameFn)(CFAllocatorRef allocator,
                                                                     const char *host);
 
-typedef Boolean (*FIRReachabilitySetCallbackFn)(SCNetworkReachabilityRef target,
+typedef Boolean (*GULReachabilitySetCallbackFn)(SCNetworkReachabilityRef target,
                                                 SCNetworkReachabilityCallBack callback,
                                                 SCNetworkReachabilityContext *context);
-typedef Boolean (*FIRReachabilityScheduleWithRunLoopFn)(SCNetworkReachabilityRef target,
+typedef Boolean (*GULReachabilityScheduleWithRunLoopFn)(SCNetworkReachabilityRef target,
                                                         CFRunLoopRef runLoop,
                                                         CFStringRef runLoopMode);
-typedef Boolean (*FIRReachabilityUnscheduleFromRunLoopFn)(SCNetworkReachabilityRef target,
+typedef Boolean (*GULReachabilityUnscheduleFromRunLoopFn)(SCNetworkReachabilityRef target,
                                                           CFRunLoopRef runLoop,
                                                           CFStringRef runLoopMode);
 
-typedef void (*FIRReachabilityReleaseFn)(CFTypeRef cf);
+typedef void (*GULReachabilityReleaseFn)(CFTypeRef cf);
 
-struct FIRReachabilityApi {
-  FIRReachabilityCreateWithNameFn createWithNameFn;
-  FIRReachabilitySetCallbackFn setCallbackFn;
-  FIRReachabilityScheduleWithRunLoopFn scheduleWithRunLoopFn;
-  FIRReachabilityUnscheduleFromRunLoopFn unscheduleFromRunLoopFn;
-  FIRReachabilityReleaseFn releaseFn;
+struct GULReachabilityApi {
+  GULReachabilityCreateWithNameFn createWithNameFn;
+  GULReachabilitySetCallbackFn setCallbackFn;
+  GULReachabilityScheduleWithRunLoopFn scheduleWithRunLoopFn;
+  GULReachabilityUnscheduleFromRunLoopFn unscheduleFromRunLoopFn;
+  GULReachabilityReleaseFn releaseFn;
 };
 
-@interface FIRReachabilityChecker (Internal)
+@interface GULReachabilityChecker (Internal)
 
-- (const struct FIRReachabilityApi *)reachabilityApi;
-- (void)setReachabilityApi:(const struct FIRReachabilityApi *)reachabilityApi;
+- (const struct GULReachabilityApi *)reachabilityApi;
+- (void)setReachabilityApi:(const struct GULReachabilityApi *)reachabilityApi;
 
 @end
diff --git a/Firebase/Core/FIRReachabilityChecker.m b/Firebase/Utilities/Reachability/GULReachabilityChecker.m
index cac87ff..1ddacdf 100644
--- a/Firebase/Core/FIRReachabilityChecker.m
+++ b/Firebase/Utilities/Reachability/GULReachabilityChecker.m
@@ -14,18 +14,20 @@
 
 #import <Foundation/Foundation.h>
 
-#import "Private/FIRReachabilityChecker+Internal.h"
-#import "Private/FIRReachabilityChecker.h"
+#import "GULReachabilityChecker+Internal.h"
+#import "Private/GULReachabilityChecker.h"
+#import "Private/GULReachabilityMessageCode.h"
 
-#import "Private/FIRLogger.h"
-#import "Private/FIRNetwork.h"
-#import "Private/FIRNetworkMessageCode.h"
+#import <GoogleUtilities/GULLogger.h>
+#import <GoogleUtilities/GULReachabilityChecker.h>
+
+static GULLoggerService kGULLoggerReachability = @"[GULReachability]";
 
 static void ReachabilityCallback(SCNetworkReachabilityRef reachability,
                                  SCNetworkReachabilityFlags flags,
                                  void *info);
 
-static const struct FIRReachabilityApi kFIRDefaultReachabilityApi = {
+static const struct GULReachabilityApi kGULDefaultReachabilityApi = {
     SCNetworkReachabilityCreateWithName,
     SCNetworkReachabilitySetCallback,
     SCNetworkReachabilityScheduleWithRunLoop,
@@ -33,36 +35,34 @@ static const struct FIRReachabilityApi kFIRDefaultReachabilityApi = {
     CFRelease,
 };
 
-static NSString *const kFIRReachabilityUnknownStatus = @"Unknown";
-static NSString *const kFIRReachabilityConnectedStatus = @"Connected";
-static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
+static NSString *const kGULReachabilityUnknownStatus = @"Unknown";
+static NSString *const kGULReachabilityConnectedStatus = @"Connected";
+static NSString *const kGULReachabilityDisconnectedStatus = @"Disconnected";
 
-@interface FIRReachabilityChecker ()
+@interface GULReachabilityChecker ()
 
-@property(nonatomic, assign) const struct FIRReachabilityApi *reachabilityApi;
-@property(nonatomic, assign) FIRReachabilityStatus reachabilityStatus;
+@property(nonatomic, assign) const struct GULReachabilityApi *reachabilityApi;
+@property(nonatomic, assign) GULReachabilityStatus reachabilityStatus;
 @property(nonatomic, copy) NSString *host;
 @property(nonatomic, assign) SCNetworkReachabilityRef reachability;
 
 @end
 
-@implementation FIRReachabilityChecker
+@implementation GULReachabilityChecker
 
 @synthesize reachabilityApi = reachabilityApi_;
 @synthesize reachability = reachability_;
 
-- (const struct FIRReachabilityApi *)reachabilityApi {
+- (const struct GULReachabilityApi *)reachabilityApi {
   return reachabilityApi_;
 }
 
-- (void)setReachabilityApi:(const struct FIRReachabilityApi *)reachabilityApi {
+- (void)setReachabilityApi:(const struct GULReachabilityApi *)reachabilityApi {
   if (reachability_) {
-    NSString *message =
-        @"Cannot change reachability API while reachability is running. "
-        @"Call stop first.";
-    [loggerDelegate_ firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeReachabilityChecker000
-                                     message:message];
+    GULLogError(kGULLoggerReachability, NO,
+                [NSString stringWithFormat:@"I-REA%06ld", (long)kGULReachabilityMessageCode000],
+                @"Cannot change reachability API while reachability is running. "
+                @"Call stop first.");
     return;
   }
   reachabilityApi_ = reachabilityApi;
@@ -71,53 +71,36 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
 @synthesize reachabilityStatus = reachabilityStatus_;
 @synthesize host = host_;
 @synthesize reachabilityDelegate = reachabilityDelegate_;
-@synthesize loggerDelegate = loggerDelegate_;
 
 - (BOOL)isActive {
   return reachability_ != nil;
 }
 
-- (void)setReachabilityDelegate:(id<FIRReachabilityDelegate>)reachabilityDelegate {
+- (void)setReachabilityDelegate:(id<GULReachabilityDelegate>)reachabilityDelegate {
   if (reachabilityDelegate &&
-      (![(NSObject *)reachabilityDelegate conformsToProtocol:@protocol(FIRReachabilityDelegate)])) {
-    FIRLogError(kFIRLoggerCore,
-                [NSString stringWithFormat:@"I-NET%06ld",
-                                           (long)kFIRNetworkMessageCodeReachabilityChecker005],
+      (![(NSObject *)reachabilityDelegate conformsToProtocol:@protocol(GULReachabilityDelegate)])) {
+    GULLogError(kGULLoggerReachability, NO,
+                [NSString stringWithFormat:@"I-NET%06ld", (long)kGULReachabilityMessageCode005],
                 @"Reachability delegate doesn't conform to Reachability protocol.");
     return;
   }
   reachabilityDelegate_ = reachabilityDelegate;
 }
 
-- (void)setLoggerDelegate:(id<FIRNetworkLoggerDelegate>)loggerDelegate {
-  if (loggerDelegate &&
-      (![(NSObject *)loggerDelegate conformsToProtocol:@protocol(FIRNetworkLoggerDelegate)])) {
-    FIRLogError(kFIRLoggerCore,
-                [NSString stringWithFormat:@"I-NET%06ld",
-                                           (long)kFIRNetworkMessageCodeReachabilityChecker006],
-                @"Reachability delegate doesn't conform to Logger protocol.");
-    return;
-  }
-  loggerDelegate_ = loggerDelegate;
-}
-
-- (instancetype)initWithReachabilityDelegate:(id<FIRReachabilityDelegate>)reachabilityDelegate
-                              loggerDelegate:(id<FIRNetworkLoggerDelegate>)loggerDelegate
+- (instancetype)initWithReachabilityDelegate:(id<GULReachabilityDelegate>)reachabilityDelegate
                                     withHost:(NSString *)host {
   self = [super init];
 
-  [self setLoggerDelegate:loggerDelegate];
-
   if (!host || !host.length) {
-    [loggerDelegate_ firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                 messageCode:kFIRNetworkMessageCodeReachabilityChecker001
-                                     message:@"Invalid host specified"];
+    GULLogError(kGULLoggerReachability, NO,
+                [NSString stringWithFormat:@"I-REA%06ld", (long)kGULReachabilityMessageCode001],
+                @"Invalid host specified");
     return nil;
   }
   if (self) {
     [self setReachabilityDelegate:reachabilityDelegate];
-    reachabilityApi_ = &kFIRDefaultReachabilityApi;
-    reachabilityStatus_ = kFIRReachabilityUnknown;
+    reachabilityApi_ = &kGULDefaultReachabilityApi;
+    reachabilityStatus_ = kGULReachabilityUnknown;
     host_ = [host copy];
     reachability_ = nil;
   }
@@ -126,7 +109,6 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
 
 - (void)dealloc {
   reachabilityDelegate_ = nil;
-  loggerDelegate_ = nil;
   [self stop];
 }
 
@@ -148,21 +130,22 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
                                                  kCFRunLoopCommonModes)) {
       reachabilityApi_->releaseFn(reachability_);
       reachability_ = nil;
-      [loggerDelegate_ firNetwork_logWithLevel:kFIRNetworkLogLevelError
-                                   messageCode:kFIRNetworkMessageCodeReachabilityChecker002
-                                       message:@"Failed to start reachability handle"];
+
+      GULLogError(kGULLoggerReachability, NO,
+                  [NSString stringWithFormat:@"I-REA%06ld", (long)kGULReachabilityMessageCode002],
+                  @"Failed to start reachability handle");
       return NO;
     }
   }
-  [loggerDelegate_ firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                               messageCode:kFIRNetworkMessageCodeReachabilityChecker003
-                                   message:@"Monitoring the network status"];
+  GULLogDebug(kGULLoggerReachability, NO,
+              [NSString stringWithFormat:@"I-REA%06ld", (long)kGULReachabilityMessageCode003],
+              @"Monitoring the network status");
   return YES;
 }
 
 - (void)stop {
   if (reachability_) {
-    reachabilityStatus_ = kFIRReachabilityUnknown;
+    reachabilityStatus_ = kGULReachabilityUnknown;
     reachabilityApi_->unscheduleFromRunLoopFn(reachability_, CFRunLoopGetMain(),
                                               kCFRunLoopCommonModes);
     reachabilityApi_->releaseFn(reachability_);
@@ -170,18 +153,18 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
   }
 }
 
-- (FIRReachabilityStatus)statusForFlags:(SCNetworkReachabilityFlags)flags {
-  FIRReachabilityStatus status = kFIRReachabilityNotReachable;
+- (GULReachabilityStatus)statusForFlags:(SCNetworkReachabilityFlags)flags {
+  GULReachabilityStatus status = kGULReachabilityNotReachable;
   // If the Reachable flag is not set, we definitely don't have connectivity.
   if (flags & kSCNetworkReachabilityFlagsReachable) {
     // Reachable flag is set. Check further flags.
     if (!(flags & kSCNetworkReachabilityFlagsConnectionRequired)) {
 // Connection required flag is not set, so we have connectivity.
 #if TARGET_OS_IOS || TARGET_OS_TV
-      status = (flags & kSCNetworkReachabilityFlagsIsWWAN) ? kFIRReachabilityViaCellular
-                                                           : kFIRReachabilityViaWifi;
+      status = (flags & kSCNetworkReachabilityFlagsIsWWAN) ? kGULReachabilityViaCellular
+                                                           : kGULReachabilityViaWifi;
 #elif TARGET_OS_OSX
-      status = kFIRReachabilityViaWifi;
+      status = kGULReachabilityViaWifi;
 #endif
     } else if ((flags & (kSCNetworkReachabilityFlagsConnectionOnDemand |
                          kSCNetworkReachabilityFlagsConnectionOnTraffic)) &&
@@ -189,10 +172,10 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
 // If the connection on demand or connection on traffic flag is set, and user intervention
 // is not required, we have connectivity.
 #if TARGET_OS_IOS || TARGET_OS_TV
-      status = (flags & kSCNetworkReachabilityFlagsIsWWAN) ? kFIRReachabilityViaCellular
-                                                           : kFIRReachabilityViaWifi;
+      status = (flags & kSCNetworkReachabilityFlagsIsWWAN) ? kGULReachabilityViaCellular
+                                                           : kGULReachabilityViaWifi;
 #elif TARGET_OS_OSX
-      status = kFIRReachabilityViaWifi;
+      status = kGULReachabilityViaWifi;
 #endif
     }
   }
@@ -200,20 +183,21 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
 }
 
 - (void)reachabilityFlagsChanged:(SCNetworkReachabilityFlags)flags {
-  FIRReachabilityStatus status = [self statusForFlags:flags];
+  GULReachabilityStatus status = [self statusForFlags:flags];
   if (reachabilityStatus_ != status) {
     NSString *reachabilityStatusString;
-    if (status == kFIRReachabilityUnknown) {
-      reachabilityStatusString = kFIRReachabilityUnknownStatus;
+    if (status == kGULReachabilityUnknown) {
+      reachabilityStatusString = kGULReachabilityUnknownStatus;
     } else {
-      reachabilityStatusString = (status == kFIRReachabilityNotReachable)
-                                     ? kFIRReachabilityDisconnectedStatus
-                                     : kFIRReachabilityConnectedStatus;
+      reachabilityStatusString = (status == kGULReachabilityNotReachable)
+                                     ? kGULReachabilityDisconnectedStatus
+                                     : kGULReachabilityConnectedStatus;
     }
-    [loggerDelegate_ firNetwork_logWithLevel:kFIRNetworkLogLevelDebug
-                                 messageCode:kFIRNetworkMessageCodeReachabilityChecker004
-                                     message:@"Network status has changed. Code, status"
-                                    contexts:@[ @(status), reachabilityStatusString ]];
+
+    GULLogDebug(kGULLoggerReachability, NO,
+                [NSString stringWithFormat:@"I-REA%06ld", (long)kGULReachabilityMessageCode004],
+                @"Network status has changed. Code:%@, status:%@", @(status),
+                reachabilityStatusString);
     reachabilityStatus_ = status;
     [reachabilityDelegate_ reachability:self statusChanged:reachabilityStatus_];
   }
@@ -224,7 +208,7 @@ static NSString *const kFIRReachabilityDisconnectedStatus = @"Disconnected";
 static void ReachabilityCallback(SCNetworkReachabilityRef reachability,
                                  SCNetworkReachabilityFlags flags,
                                  void *info) {
-  FIRReachabilityChecker *checker = (__bridge FIRReachabilityChecker *)info;
+  GULReachabilityChecker *checker = (__bridge GULReachabilityChecker *)info;
   [checker reachabilityFlagsChanged:flags];
 }
 
@@ -236,18 +220,18 @@ static void ReachabilityCallback(SCNetworkReachabilityRef reachability,
 // discovered that moving this function to the end of the file magically fixed
 // the crash. If you are going to edit this file, exercise caution and make sure
 // to test thoroughly with an iOS device under various network conditions.
-const NSString *FIRReachabilityStatusString(FIRReachabilityStatus status) {
+const NSString *GULReachabilityStatusString(GULReachabilityStatus status) {
   switch (status) {
-    case kFIRReachabilityUnknown:
+    case kGULReachabilityUnknown:
       return @"Reachability Unknown";
 
-    case kFIRReachabilityNotReachable:
+    case kGULReachabilityNotReachable:
       return @"Not reachable";
 
-    case kFIRReachabilityViaWifi:
+    case kGULReachabilityViaWifi:
       return @"Reachable via Wifi";
 
-    case kFIRReachabilityViaCellular:
+    case kGULReachabilityViaCellular:
       return @"Reachable via Cellular Data";
 
     default:
diff --git a/Firebase/Core/Private/FIRReachabilityChecker.h b/Firebase/Utilities/Reachability/Private/GULReachabilityChecker.h
index 3a6a531..b317a0b 100644
--- a/Firebase/Core/Private/FIRReachabilityChecker.h
+++ b/Firebase/Utilities/Reachability/Private/GULReachabilityChecker.h
@@ -19,37 +19,34 @@
 
 /// Reachability Status
 typedef enum {
-  kFIRReachabilityUnknown,  ///< Have not yet checked or been notified whether host is reachable.
-  kFIRReachabilityNotReachable,  ///< Host is not reachable.
-  kFIRReachabilityViaWifi,       ///< Host is reachable via Wifi.
-  kFIRReachabilityViaCellular,   ///< Host is reachable via cellular.
-} FIRReachabilityStatus;
+  kGULReachabilityUnknown,  ///< Have not yet checked or been notified whether host is reachable.
+  kGULReachabilityNotReachable,  ///< Host is not reachable.
+  kGULReachabilityViaWifi,       ///< Host is reachable via Wifi.
+  kGULReachabilityViaCellular,   ///< Host is reachable via cellular.
+} GULReachabilityStatus;
 
-const NSString *FIRReachabilityStatusString(FIRReachabilityStatus status);
+const NSString *GULReachabilityStatusString(GULReachabilityStatus status);
 
-@class FIRReachabilityChecker;
-@protocol FIRNetworkLoggerDelegate;
+@class GULReachabilityChecker;
 
 /// Google Analytics iOS Reachability Checker.
-@protocol FIRReachabilityDelegate
+@protocol GULReachabilityDelegate
 @required
 /// Called when network status has changed.
-- (void)reachability:(FIRReachabilityChecker *)reachability
-       statusChanged:(FIRReachabilityStatus)status;
+- (void)reachability:(GULReachabilityChecker *)reachability
+       statusChanged:(GULReachabilityStatus)status;
 @end
 
 /// Google Analytics iOS Network Status Checker.
-@interface FIRReachabilityChecker : NSObject
+@interface GULReachabilityChecker : NSObject
 
-/// The last known reachability status, or FIRReachabilityStatusUnknown if the
+/// The last known reachability status, or GULReachabilityStatusUnknown if the
 /// checker is not active.
-@property(nonatomic, readonly) FIRReachabilityStatus reachabilityStatus;
+@property(nonatomic, readonly) GULReachabilityStatus reachabilityStatus;
 /// The host to which reachability status is to be checked.
 @property(nonatomic, copy, readonly) NSString *host;
 /// The delegate to be notified of reachability status changes.
-@property(nonatomic, weak) id<FIRReachabilityDelegate> reachabilityDelegate;
-/// The delegate to be notified to log messages.
-@property(nonatomic, weak) id<FIRNetworkLoggerDelegate> loggerDelegate;
+@property(nonatomic, weak) id<GULReachabilityDelegate> reachabilityDelegate;
 /// `YES` if the reachability checker is active, `NO` otherwise.
 @property(nonatomic, readonly) BOOL isActive;
 
@@ -59,12 +56,9 @@ const NSString *FIRReachabilityStatusString(FIRReachabilityStatus status);
 /// @param reachabilityDelegate The delegate to be notified when reachability status to host
 /// changes.
 ///
-/// @param loggerDelegate The delegate to send log messages to.
-///
 /// @param host The name of the host.
 ///
-- (instancetype)initWithReachabilityDelegate:(id<FIRReachabilityDelegate>)reachabilityDelegate
-                              loggerDelegate:(id<FIRNetworkLoggerDelegate>)loggerDelegate
+- (instancetype)initWithReachabilityDelegate:(id<GULReachabilityDelegate>)reachabilityDelegate
                                     withHost:(NSString *)host;
 
 - (instancetype)init NS_UNAVAILABLE;
diff --git a/Firebase/Utilities/Reachability/Private/GULReachabilityMessageCode.h b/Firebase/Utilities/Reachability/Private/GULReachabilityMessageCode.h
new file mode 100644
index 0000000..283cdd5
--- /dev/null
+++ b/Firebase/Utilities/Reachability/Private/GULReachabilityMessageCode.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Make sure these codes do not overlap with any contained in the FIRAMessageCode enum.
+typedef NS_ENUM(NSInteger, GULReachabilityMessageCode) {
+  // GULReachabilityChecker.m
+  kGULReachabilityMessageCode000 = 902000,  // I-NET902000
+  kGULReachabilityMessageCode001 = 902001,  // I-NET902001
+  kGULReachabilityMessageCode002 = 902002,  // I-NET902002
+  kGULReachabilityMessageCode003 = 902003,  // I-NET902003
+  kGULReachabilityMessageCode004 = 902004,  // I-NET902004
+  kGULReachabilityMessageCode005 = 902005,  // I-NET902005
+  kGULReachabilityMessageCode006 = 902006,  // I-NET902006
+};
diff --git a/FirebaseAuth.podspec b/FirebaseAuth.podspec
index 43c565f..47e211b 100644
--- a/FirebaseAuth.podspec
+++ b/FirebaseAuth.podspec
@@ -62,5 +62,6 @@ supports email and password accounts, as well as several 3rd party authenticatio
   s.framework = 'SafariServices'
   s.framework = 'Security'
   s.dependency 'FirebaseCore', '~> 5.0'
+  s.dependency 'GoogleUtilities/Environment', '~> 5.0'
   s.dependency 'GTMSessionFetcher/Core', '~> 1.1'
 end
diff --git a/FirebaseCore.podspec b/FirebaseCore.podspec
index 8aa0b23..9d6fccf 100644
--- a/FirebaseCore.podspec
+++ b/FirebaseCore.podspec
@@ -13,7 +13,9 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
 
   s.source           = {
     :git => 'https://github.com/firebase/firebase-ios-sdk.git',
-    :tag => 'Core-' + s.version.to_s
+# Undo comment before release
+#    :tag => 'Core-' + s.version.to_s
+    :tag => 'pre-5.3-' + s.version.to_s
   }
   s.social_media_url = 'https://twitter.com/Firebase'
   s.ios.deployment_target = '8.0'
@@ -26,12 +28,11 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
 
   s.source_files = 'Firebase/Core/**/*.[mh]'
   s.public_header_files = 'Firebase/Core/Public/*.h', 'Firebase/Core/Private/*.h'
-  s.private_header_files = 'Firebase/Core/Private/*.h', 'Firebase/Core/third_party/*.h'
+  s.private_header_files = 'Firebase/Core/Private/*.h'
   s.frameworks = [
-    'Foundation',
-    'SystemConfiguration'
+    'Foundation'
   ]
-  s.dependency 'GoogleToolboxForMac/NSData+zlib', '~> 2.1'
+  s.dependency 'GoogleUtilities/Logger', '~> 5.0'
   s.pod_target_xcconfig = {
     'OTHER_CFLAGS' => '-fno-autolink',
     'GCC_PREPROCESSOR_DEFINITIONS' =>
diff --git a/FirebaseMessaging.podspec b/FirebaseMessaging.podspec
index 77ec0b3..cb8737f 100644
--- a/FirebaseMessaging.podspec
+++ b/FirebaseMessaging.podspec
@@ -38,6 +38,6 @@ device, and it is completely free.
   s.framework = 'SystemConfiguration'
   s.dependency 'FirebaseCore', '~> 5.0'
   s.dependency 'FirebaseInstanceID', '~> 3.0'
-  s.dependency 'GoogleToolboxForMac/Logger', '~> 2.1'
+  s.dependency 'GoogleUtilities/Reachability', '~> 5.0'
   s.dependency 'Protobuf', '~> 3.1'
 end
diff --git a/Firestore/CMakeLists.txt b/Firestore/CMakeLists.txt
index d5027ce..c74313c 100644
--- a/Firestore/CMakeLists.txt
+++ b/Firestore/CMakeLists.txt
@@ -85,6 +85,7 @@ find_package(Protobuf REQUIRED)
 find_package(GRPC REQUIRED)
 
 if(APPLE)
+  find_package(GoogleUtilities REQUIRED)
   find_package(FirebaseCore REQUIRED)
 endif()
 
diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index d15e590..7aef00c 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -1429,7 +1429,6 @@
 				"${SRCROOT}/Pods/Target Support Files/Pods-Firestore_Example_iOS-SwiftBuildTest/Pods-Firestore_Example_iOS-SwiftBuildTest-frameworks.sh",
 				"${BUILT_PRODUCTS_DIR}/BoringSSL/openssl.framework",
 				"${BUILT_PRODUCTS_DIR}/GTMSessionFetcher/GTMSessionFetcher.framework",
-				"${BUILT_PRODUCTS_DIR}/GoogleToolboxForMac/GoogleToolboxForMac.framework",
 				"${BUILT_PRODUCTS_DIR}/Protobuf/Protobuf.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC/GRPCClient.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC-Core/grpc.framework",
@@ -1442,7 +1441,6 @@
 			outputPaths = (
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/openssl.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GTMSessionFetcher.framework",
-				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GoogleToolboxForMac.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/Protobuf.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GRPCClient.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/grpc.framework",
@@ -1465,7 +1463,6 @@
 				"${SRCROOT}/Pods/Target Support Files/Pods-Firestore_Example_iOS/Pods-Firestore_Example_iOS-frameworks.sh",
 				"${BUILT_PRODUCTS_DIR}/BoringSSL/openssl.framework",
 				"${BUILT_PRODUCTS_DIR}/GTMSessionFetcher/GTMSessionFetcher.framework",
-				"${BUILT_PRODUCTS_DIR}/GoogleToolboxForMac/GoogleToolboxForMac.framework",
 				"${BUILT_PRODUCTS_DIR}/Protobuf/Protobuf.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC/GRPCClient.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC-Core/grpc.framework",
@@ -1478,7 +1475,6 @@
 			outputPaths = (
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/openssl.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GTMSessionFetcher.framework",
-				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GoogleToolboxForMac.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/Protobuf.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GRPCClient.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/grpc.framework",
@@ -1669,7 +1665,6 @@
 				"${SRCROOT}/Pods/Target Support Files/Pods-Firestore_Example_iOS-Firestore_SwiftTests_iOS/Pods-Firestore_Example_iOS-Firestore_SwiftTests_iOS-frameworks.sh",
 				"${BUILT_PRODUCTS_DIR}/BoringSSL/openssl.framework",
 				"${BUILT_PRODUCTS_DIR}/GTMSessionFetcher/GTMSessionFetcher.framework",
-				"${BUILT_PRODUCTS_DIR}/GoogleToolboxForMac/GoogleToolboxForMac.framework",
 				"${BUILT_PRODUCTS_DIR}/Protobuf/Protobuf.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC/GRPCClient.framework",
 				"${BUILT_PRODUCTS_DIR}/gRPC-Core/grpc.framework",
@@ -1682,7 +1677,6 @@
 			outputPaths = (
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/openssl.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GTMSessionFetcher.framework",
-				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GoogleToolboxForMac.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/Protobuf.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/GRPCClient.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/grpc.framework",
diff --git a/Firestore/Example/Podfile b/Firestore/Example/Podfile
index 3095b19..86cbd82 100644
--- a/Firestore/Example/Podfile
+++ b/Firestore/Example/Podfile
@@ -10,10 +10,11 @@ target 'Firestore_Example_iOS' do
   # The next line is the forcing function for the Firebase pod. The Firebase
   # version's subspecs should depend on the component versions in their
   # corresponding podspec's.
-  pod 'Firebase/Core', '5.4.0'
+  pod 'Firebase/CoreOnly', '5.4.0'
 
   pod 'FirebaseAuth', :path => '../../'
   pod 'FirebaseCore', :path => '../../'
+  pod 'GoogleUtilities', :path => '../../'
   pod 'FirebaseFirestore', :path => '../../'
 
   target 'Firestore_Tests_iOS' do
diff --git a/Firestore/core/src/firebase/firestore/auth/CMakeLists.txt b/Firestore/core/src/firebase/firestore/auth/CMakeLists.txt
index 2241fae..92f1de1 100644
--- a/Firestore/core/src/firebase/firestore/auth/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/auth/CMakeLists.txt
@@ -33,6 +33,7 @@ cc_library(
     firebase_credentials_provider_apple.mm
   DEPENDS
     FirebaseCore
+    GoogleUtilities
     firebase_firestore_auth_base
   EXCLUDE_FROM_ALL
 )
diff --git a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
index 5b38b2e..228b0c0 100644
--- a/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/util/CMakeLists.txt
@@ -55,6 +55,7 @@ cc_library(
     string_apple.h
   DEPENDS
     FirebaseCore
+    GoogleUtilities
     absl_strings
     firebase_firestore_util_base
   EXCLUDE_FROM_ALL
diff --git a/Firestore/core/test/firebase/firestore/testutil/CMakeLists.txt b/Firestore/core/test/firebase/firestore/testutil/CMakeLists.txt
index 636acb0..9d6e4a7 100644
--- a/Firestore/core/test/firebase/firestore/testutil/CMakeLists.txt
+++ b/Firestore/core/test/firebase/firestore/testutil/CMakeLists.txt
@@ -19,6 +19,7 @@ cc_library(
     app_testing.mm
   DEPENDS
     FirebaseCore
+    GoogleUtilities
     absl_strings
   EXCLUDE_FROM_ALL
 )
diff --git a/Functions/Example/Podfile b/Functions/Example/Podfile
index ea07e11..6761062 100644
--- a/Functions/Example/Podfile
+++ b/Functions/Example/Podfile
@@ -4,6 +4,7 @@ target 'FirebaseFunctions_Example' do
   platform :ios, '8.0'
 
   pod 'FirebaseCore', :path => '../../'
+  pod 'GoogleUtilities', :path => '../../'
   pod 'FirebaseFunctions', :path => '../../'
 
   target 'FirebaseFunctions_Tests' do
diff --git a/GoogleUtilities.podspec b/GoogleUtilities.podspec
new file mode 100644
index 0000000..2dd72f3
--- /dev/null
+++ b/GoogleUtilities.podspec
@@ -0,0 +1,71 @@
+Pod::Spec.new do |s|
+  s.name             = 'GoogleUtilities'
+  s.version          = '5.0.5'
+  s.summary          = 'Google Utilities for iOS (plus community support for macOS and tvOS)'
+
+  s.description      = <<-DESC
+Internal Google Utilities including Network, Reachability Environment, Logger, and Swizzling for
+other Google CocoaPods. They're not intended for direct public usage.
+                       DESC
+
+# TODO update homepage link with GoogleUtilities is moved to another repo.
+  s.homepage         = 'https://github.com/firebase/firebase-ios-sdk'
+  s.license          = { :type => 'Apache', :file => 'LICENSE' }
+  s.authors          = 'Google, Inc.'
+
+  s.source           = {
+    :git => 'https://github.com/firebase/firebase-ios-sdk.git',
+# Undo comment before release.
+#    :tag => 'Utilities-' + s.version.to_s
+    :tag => 'pre-5.3-' + s.version.to_s
+  }
+  s.ios.deployment_target = '6.0'
+  s.osx.deployment_target = '10.10'
+  s.tvos.deployment_target = '10.0'
+
+  s.cocoapods_version = '>= 1.4.0'
+  s.prefix_header_file = false
+
+  s.subspec 'Environment' do |es|
+    es.source_files = 'Firebase/Utilities/Environment/third_party/*.[mh]'
+    es.public_header_files = 'Firebase/Utilities/Environment/third_party/*.h'
+    es.private_header_files = 'Firebase/Utilities/Environment/third_party/*.h'
+  end
+
+  s.subspec 'Logger' do |ls|
+    ls.source_files = 'Firebase/Utilities/Logger/**/*.[mh]'
+    ls.public_header_files = 'Firebase/Utilities/Logger/Private/*.h', 'Firebase/Utilities/Logger/Public/*.h'
+    ls.private_header_files = 'Firebase/Utilities/Logger/Private/*.h'
+    ls.dependency 'GoogleUtilities/Environment'
+  end
+
+  s.subspec 'Network' do |ns|
+    ns.source_files = 'Firebase/Utilities/Network/**/*.[mh]'
+    ns.public_header_files = 'Firebase/Utilities/Network/Private/*.h'
+    ns.private_header_files = 'Firebase/Utilities/Network/Private/*.h'
+    ns.dependency 'GoogleUtilities/NSData+zlib'
+    ns.dependency 'GoogleUtilities/Logger'
+    ns.dependency 'GoogleUtilities/Reachability'
+    ns.frameworks = [
+      'Security'
+    ]
+  end
+
+  s.subspec 'NSData+zlib' do |ns|
+    ns.source_files = 'Firebase/Utilities/NSData+zlib/*.[mh]'
+    ns.public_header_files = 'Firebase/Utilities/NSData+zlib/GULNSData+zlib.h'
+    ns.libraries = [
+      'z'
+    ]
+  end
+
+  s.subspec 'Reachability' do |rs|
+    rs.source_files = 'Firebase/Utilities/Reachability/**/*.[mh]'
+    rs.public_header_files = 'Firebase/Utilities/Reachability/Private/*.h'
+    rs.private_header_files = 'Firebase/Utilities/Reachability/Private/*.h'
+    rs.frameworks = [
+      'SystemConfiguration'
+    ]
+    rs.dependency 'GoogleUtilities/Logger'
+  end
+end
diff --git a/cmake/FindGoogleUtilities.cmake b/cmake/FindGoogleUtilities.cmake
new file mode 100644
index 0000000..37f7361
--- /dev/null
+++ b/cmake/FindGoogleUtilities.cmake
@@ -0,0 +1,56 @@
+# Copyright 2018 Google
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+find_library(
+  GoogleUtilities_LIBRARY
+  GoogleUtilities
+  PATHS ${FIREBASE_INSTALL_DIR}/Frameworks
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(
+  GoogleUtilities
+  DEFAULT_MSG
+  GoogleUtilities_LIBRARY
+)
+
+if(GoogleUtilities_FOUND)
+  # Emulate CocoaPods behavior which makes all headers available unqualified.
+  set(
+    GoogleUtilities_INCLUDE_DIRS
+    ${GoogleUtilities_LIBRARY}/Headers
+    ${GoogleUtilities_LIBRARY}/PrivateHeaders
+  )
+
+  set(
+    GoogleUtilities_LIBRARIES
+    ${GoogleUtilities_LIBRARY}
+    "-framework Foundation"
+  )
+
+  if(NOT TARGET GoogleUtilities)
+    # Add frameworks as INTERFACE libraries rather than IMPORTED so that
+    # framework behavior is preserved.
+    add_library(GoogleUtilities INTERFACE)
+
+    set_property(
+      TARGET GoogleUtilities APPEND PROPERTY
+      INTERFACE_INCLUDE_DIRECTORIES ${GoogleUtilities_INCLUDE_DIRS}
+    )
+    set_property(
+      TARGET GoogleUtilities APPEND PROPERTY
+      INTERFACE_LINK_LIBRARIES ${GoogleUtilities_LIBRARIES}
+    )
+  endif()
+endif(GoogleUtilities_FOUND)
diff --git a/cmake/external/GoogleUtilities.cmake b/cmake/external/GoogleUtilities.cmake
new file mode 100644
index 0000000..af90001
--- /dev/null
+++ b/cmake/external/GoogleUtilities.cmake
@@ -0,0 +1,23 @@
+# Copyright 2018 Google
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+include(xcodebuild)
+
+if(APPLE)
+  # GoogleUtilities is only available as a CocoaPod build.
+  xcodebuild(GoogleUtilities)
+else()
+  # On non-Apple platforms, there's no way to build GoogleUtilities.
+  add_custom_target(GoogleUtilities)
+endif()