diff --git a/.github/workflows/api_report.yml b/.github/workflows/api_report.yml
index c981d2ee3db..bd30b61d9b0 100644
--- a/.github/workflows/api_report.yml
+++ b/.github/workflows/api_report.yml
@@ -12,14 +12,41 @@ jobs:
 
       - name: Checkout PR branch
         uses: actions/checkout@v3
+        with:
+          fetch-depth: 2
+
+      - id: get_changed_files
+        run: echo "file_list=$(git diff --name-only -r HEAD^1 HEAD | tr '\n' ' ')" >> $GITHUB_OUTPUT
+        
+      - name: Setup python
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.7
 
-      - name: Make diff directory
-        run: mkdir ~/diff
+      - name: Copy script
+        run: |
+          cp scripts/api_diff_report/api_info.py ~/api_info.py
+          cp scripts/api_diff_report/api_diff.py ~/api_diff.py
 
-      - name: List changed files
-        run: git diff --name-only ${{ github.base_ref }})
+      - name: Generate API files for PR branch
+        run: python ~/api_info.py -f ${{ steps.get_changed_files.outputs.file_list }} -o "~/merge_branch"
 
       - name: Checkout master
         uses: actions/checkout@v3
         with:
           ref: ${{ github.base_ref }}
+
+      - name: Generate API files for Base branch
+        run: python ~/api_info.py -f ${{ steps.get_changed_files.outputs.file_list }} -o "~/base_branch"
+
+      - name: Diff
+        run: python ~/api_diff.py -m "~/merge_branch" -b "~/base_branch"
+
+      - uses: actions/upload-artifact@v3
+        if: ${{ !cancelled() }}
+        with:
+          name: api_info
+          path: | 
+            ~/merge_branch
+            ~/base_branch
+          retention-days: 1
diff --git a/FirebaseAppDistribution/Sources/Public/FirebaseAppDistribution/FIRAppDistribution.h b/FirebaseAppDistribution/Sources/Public/FirebaseAppDistribution/FIRAppDistribution.h
index 3b491729805..ff0553414f6 100644
--- a/FirebaseAppDistribution/Sources/Public/FirebaseAppDistribution/FIRAppDistribution.h
+++ b/FirebaseAppDistribution/Sources/Public/FirebaseAppDistribution/FIRAppDistribution.h
@@ -41,14 +41,13 @@ NS_SWIFT_NAME(AppDistribution)
 /**
  * Sign-in the App Distribution tester
  */
-- (void)signInTesterWithCompletion:(void (^)(NSError *_Nullable error))completion
+- (void)signInTesterWithCompletion:(void (^)(NSError * error))completion
     NS_SWIFT_NAME(signInTester(completion:));
 
 /**
  * Check to see whether a new distribution is available
  */
-- (void)checkForUpdateWithCompletion:(void (^)(FIRAppDistributionRelease *_Nullable_result release,
-                                               NSError *_Nullable error))completion
+- (void)checkForUpdateWithCompletion:(void (^)(FIRAppDistributionRelease *_Nullable_result release))completion
     NS_SWIFT_NAME(checkForUpdate(completion:));
 
 /**
diff --git a/FirebaseCore/Sources/Public/FirebaseCore/FIRApp.h b/FirebaseCore/Sources/Public/FirebaseCore/FIRApp.h
index 58ef2a62594..3122d35938e 100644
--- a/FirebaseCore/Sources/Public/FirebaseCore/FIRApp.h
+++ b/FirebaseCore/Sources/Public/FirebaseCore/FIRApp.h
@@ -24,6 +24,9 @@ NS_ASSUME_NONNULL_BEGIN
 typedef void (^FIRAppVoidBoolCallback)(BOOL success)
     NS_SWIFT_UNAVAILABLE("Use Swift's closure syntax instead.");
 
+typedef void (^FIRAppVoidBoolCallbackTest)(BOOL success)
+    NS_SWIFT_UNAVAILABLE("Use Swift's closure syntax instead.");
+
 /**
  * The entry point of Firebase SDKs.
  *
@@ -61,7 +64,7 @@ NS_SWIFT_NAME(FirebaseApp)
  *
  * @param options The Firebase application options used to configure the service.
  */
-+ (void)configureWithOptions:(FIROptions *)options NS_SWIFT_NAME(configure(options:));
++ (void)configureWithOptions:(FIROptions *__nullable)options NS_SWIFT_NAME(configure(options:));
 
 /**
  * Configures a Firebase app with the given name and options. Raises an exception if any
diff --git a/FirebaseCore/Sources/Public/FirebaseCore/FIRLoggerLevel.h b/FirebaseCore/Sources/Public/FirebaseCore/FIRLoggerLevel.h
index dca3aa0b01f..5582f3fd487 100644
--- a/FirebaseCore/Sources/Public/FirebaseCore/FIRLoggerLevel.h
+++ b/FirebaseCore/Sources/Public/FirebaseCore/FIRLoggerLevel.h
@@ -21,6 +21,7 @@
  * The log levels used by internal logging.
  */
 typedef NS_ENUM(NSInteger, FIRLoggerLevel) {
+  FIRLoggerLevelTest = 999,
   /** Error level, matches ASL_LEVEL_ERR. */
   FIRLoggerLevelError = 3,
   /** Warning level, matches ASL_LEVEL_WARNING. */
diff --git a/FirebaseCore/Sources/Public/FirebaseCore/FIRVersion.h b/FirebaseCore/Sources/Public/FirebaseCore/FIRVersion.h
index 651edaf5c8b..217f8b8aeb0 100644
--- a/FirebaseCore/Sources/Public/FirebaseCore/FIRVersion.h
+++ b/FirebaseCore/Sources/Public/FirebaseCore/FIRVersion.h
@@ -20,6 +20,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 /** Returns the current version of Firebase. */
 NS_SWIFT_NAME(FirebaseVersion())
-NSString* FIRFirebaseVersion(void);
+NSString* FIRFirebaseVersion(NSString *);
 
 NS_ASSUME_NONNULL_END
diff --git a/FirebaseMLModelDownloader/Sources/ModelDownloadTask.swift b/FirebaseMLModelDownloader/Sources/ModelDownloadTask.swift
index 05256933f29..b3be129303d 100644
--- a/FirebaseMLModelDownloader/Sources/ModelDownloadTask.swift
+++ b/FirebaseMLModelDownloader/Sources/ModelDownloadTask.swift
@@ -15,7 +15,7 @@
 import Foundation
 
 /// Task to download model file to device.
-class ModelDownloadTask {
+public final class ModelDownloadTask {
   /// Name of the app associated with this instance of ModelDownloadTask.
   private let appName: String
 
diff --git a/FirebaseMLModelDownloader/Sources/ModelDownloader.swift b/FirebaseMLModelDownloader/Sources/ModelDownloader.swift
index 6094ae02b9e..55702a5abef 100644
--- a/FirebaseMLModelDownloader/Sources/ModelDownloader.swift
+++ b/FirebaseMLModelDownloader/Sources/ModelDownloader.swift
@@ -96,13 +96,21 @@ public class ModelDownloader {
   }
 
   /// Model downloader with default app.
-  public static func modelDownloader() -> ModelDownloader {
+  public static func modelDownloader() -> ModelDownloader? {
     guard let defaultApp = FirebaseApp.app() else {
       fatalError(ModelDownloader.ErrorDescription.defaultAppNotConfigured)
     }
     return modelDownloader(app: defaultApp)
   }
 
+  /// Model downloader with default app.
+  public static func modelDownloaderNullable() -> ModelDownloader? {
+    guard let defaultApp = FirebaseApp.app() else {
+      fatalError(ModelDownloader.ErrorDescription.defaultAppNotConfigured)
+    }
+    return nil
+  }
+
   /// Model Downloader with custom app.
   public static func modelDownloader(app: FirebaseApp) -> ModelDownloader {
     if let downloader = modelDownloaderDictionary[app.name] {
diff --git a/scripts/api_diff_report/api_diff.py b/scripts/api_diff_report/api_diff.py
new file mode 100644
index 00000000000..f479a4d7933
--- /dev/null
+++ b/scripts/api_diff_report/api_diff.py
@@ -0,0 +1,167 @@
+# Copyright 2023 Google LLC
+#
+# 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 json
+import argparse
+import logging
+import os 
+import subprocess
+
+OBJC_EXTENSION = "h"
+SWIFT_EXTENSION = "swift"
+
+KEY_KIND = {
+  "source.lang.swift.decl.function.method.instance": "",
+  "source.lang.swift.decl.function.method.static": "static"
+}
+
+def main():
+  logging.getLogger().setLevel(logging.INFO)
+
+  args = parse_cmdline_args()
+  logging.info(args)
+  
+  merged_branch = os.path.expanduser(args.merged_branch)
+  base_branch = os.path.expanduser(args.base_branch)
+  
+  for file_name in os.listdir(merged_branch):
+    logging.info(f"\n\nDetect API changes in {file_name}")
+    merged_file = os.path.join(merged_branch, file_name)
+    base_file = os.path.join(base_branch, file_name)
+    api_diff(merged_file, base_file)
+    text_diff(merged_file, base_file)
+
+
+def text_diff(merged_file, base_file):
+  result = subprocess.Popen(f"git diff --no-index --word-diff {merged_file} {base_file}", 
+                            universal_newlines=True, 
+                            shell=True, 
+                            stdout=subprocess.PIPE)
+  logging.info("------------")
+  api_info = result.stdout.read()
+  logging.info(api_info)
+
+
+def api_diff(merged_file, base_file):
+  file_extension = merged_file.split(".")[1]
+  if file_extension == OBJC_EXTENSION:
+    pr_apis = get_objc_public_apis(json.load(open(merged_file)))
+    base_apis = get_objc_public_apis(json.load(open(base_file)))
+
+    pr_only_apis = get_objc_diff(pr_apis, base_apis)
+    base_only_apis = get_objc_diff(base_apis, pr_apis)
+    logging.info("Added APIs")
+    print_objc_diff(pr_only_apis)
+    logging.info("\nRemoved APIS")
+    print_objc_diff(base_only_apis)
+  elif file_extension == SWIFT_EXTENSION:
+    pr_apis = get_swift_public_apis(json.load(open(merged_file)))
+    base_apis = get_swift_public_apis(json.load(open(base_file)))
+
+    pr_only_apis = get_swift_diff(pr_apis, base_apis)
+    base_only_apis = get_swift_diff(base_apis, pr_apis)
+    logging.info("Added APIs")
+    print_swift_diff(pr_only_apis)
+    logging.info("\nRemoved APIS")
+    print_swift_diff(base_only_apis)
+
+
+def get_swift_public_apis(api_json):
+  # key: file name
+  # value: all classes and functions
+  # only one key, value pair
+  for key, value in api_json.items():
+    # filter out non-public classes
+    public_apis = [sc for sc in value["key.substructure"] if "key.accessibility" in sc and sc["key.accessibility"] == "source.lang.swift.accessibility.public"]
+    for sc in public_apis:
+      # filter out non-public functions
+      sc["key.substructure"] = [f for f in sc["key.substructure"] if "key.accessibility" in f and f["key.accessibility"] == "source.lang.swift.accessibility.public"]
+  return public_apis
+
+
+def get_swift_diff(target, base):
+  diff = {"class":[], "function":[]}
+
+  for tc in target:
+    for bc in base:
+      # check for same public classes
+      if tc["key.kind"] == bc["key.kind"] and tc["key.name"] == bc["key.name"]:
+        # check for same public functions
+        for tf in tc["key.substructure"]:
+          if "key.typename" in tf:
+            for bf in bc["key.substructure"]:
+              if tf["key.kind"] == bf["key.kind"] and tf["key.name"] == bf["key.name"] and tf["key.typename"] == bf["key.typename"]:
+                break
+            else:
+              diff["function"].append(tf)
+        break
+    else:
+      diff["class"].append(tc)
+  return diff
+
+
+def print_swift_diff(diff):
+  for c in diff["class"]:
+    logging.info(f'{c["key.name"]}')
+  for f in diff["function"]:
+    logging.info(f'Function: public {KEY_KIND[f["key.kind"]]} func {f["key.name"]} -> {f["key.typename"]}')
+
+
+def get_objc_public_apis(api_json):
+  for key, value in api_json[0].items():
+    return value["key.substructure"]
+
+
+def get_objc_diff(target, base):
+  diff = {"class":[], "function":[]}
+
+  for tc in target:
+    for bc in base:
+      # check for same public classes
+      if tc["key.kind"] == bc["key.kind"] and tc["key.name"] == bc["key.name"] and tc["key.parsed_declaration"] == bc["key.parsed_declaration"]:
+        # check for same public functions
+        if "key.substructure" in tc:
+          for tf in tc["key.substructure"]:
+            for bf in bc["key.substructure"]:
+              if tf["key.kind"] == bf["key.kind"] and tf["key.name"] == bf["key.name"] and tf["key.parsed_declaration"] == bf["key.parsed_declaration"]:
+                break
+            else:
+              diff["function"].append(tf)
+        break
+    else:
+      diff["class"].append(tc)
+  return diff
+
+
+def print_objc_diff(diff):
+  for c in diff["class"]:
+    logging.info(f'Class: {c["key.kind"]} {c["key.name"]}')
+  for f in diff["function"]:
+    logging.info(f'OBJC Function: {f["key.parsed_declaration"]}')
+  for f in diff["function"]:
+    if "key.swift_declaration" in f:
+      logging.info(f'SWIFT Function: {f["key.swift_declaration"]}')
+
+
+def parse_cmdline_args():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('-m', '--merged_branch')
+  parser.add_argument('-b', '--base_branch')
+
+  args = parser.parse_args()
+  return args
+
+
+if __name__ == '__main__':
+  main()
\ No newline at end of file
diff --git a/scripts/api_diff_report/api_info.py b/scripts/api_diff_report/api_info.py
new file mode 100644
index 00000000000..4abebfe77bd
--- /dev/null
+++ b/scripts/api_diff_report/api_info.py
@@ -0,0 +1,141 @@
+# Copyright 2023 Google LLC
+#
+# 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 json
+import argparse
+import logging
+import os 
+import subprocess
+import re
+
+PRODUCT_LIST = [
+  "ABTesting",
+  "AppCheck",
+  "AppDistribution",
+  "Analytics",
+  "Authentication",
+  "Core",
+  "Crashlytics",
+  "Database",
+  "DynamicLinks",
+  "Firestore",
+  "Functions",
+  "InAppMessaging",
+  "Installations",
+  "Messaging",
+  "Performance",
+  "RemoteConfig",
+  "Storage"
+]
+
+def main():
+  logging.getLogger().setLevel(logging.INFO)
+
+  args = parse_cmdline_args()
+  logging.info(args)
+  
+  output_dir = os.path.expanduser(args.output_dir)
+  isExist = os.path.exists(output_dir)
+  if not isExist:
+    os.makedirs(output_dir)
+  
+  swift_to_objc = {}
+  for file_path in args.file_list:
+    logging.info(file_path)
+    if file_path.endswith('.swift'):
+      result = subprocess.Popen(f"sourcekitten doc --single-file {file_path}", 
+                                universal_newlines=True, 
+                                shell=True, 
+                                stdout=subprocess.PIPE)
+      logging.info("------------")
+      api_info = result.stdout.read()
+      output_path = os.path.join(output_dir, os.path.basename(file_path) + ".json")
+      logging.info(output_path)
+      with open(output_path, 'w') as f:
+        f.write(api_info)
+
+      match = re.search(fr"Firebase(.*?){os.sep}", file_path)
+      if match:
+        scheme = f"Firebase{match.groups()[0]}"
+        if scheme not in swift_to_objc:
+          swift_to_objc[scheme] = f"{scheme}-Swift.h"
+      else:
+        logging.error(f"no target matching file: {file_path}")
+    elif file_path.endswith('.h') and "Public" in file_path:
+      result = subprocess.Popen(f"sourcekitten doc --objc {file_path} -- -x objective-c -isysroot $(xcrun --show-sdk-path) -I $(pwd)", 
+                                universal_newlines=True, 
+                                shell=True, 
+                                stdout=subprocess.PIPE)
+      logging.info("------------")
+      api_info = result.stdout.read()
+      output_path = os.path.join(output_dir, os.path.basename(file_path) + ".json")
+      logging.info(output_path)
+      with open(output_path, 'w') as f:
+        f.write(api_info)
+
+  for scheme, objc_header in swift_to_objc.items():
+    result = subprocess.Popen("scripts/setup_spm_tests.sh", 
+                              universal_newlines=True, 
+                              shell=True, 
+                              stdout=subprocess.PIPE)
+    logging.info("------------")
+    build_info = result.stdout.read()
+    logging.info(build_info)
+    derived_data_location = os.path.expanduser(f"~/{args.output_dir}/{scheme}/build/")
+    subprocess.Popen(f"defaults write com.apple.dt.Xcode IDECustomDerivedDataLocation {derived_data_location}", 
+                                    universal_newlines=True, 
+                                    shell=True, 
+                                    stdout=subprocess.PIPE)
+    
+    result = subprocess.Popen(f"xcodebuild -scheme {scheme} -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone 11' ONLY_ACTIVE_ARCH=YES CODE_SIGNING_REQUIRED=NO CODE_SIGNING_ALLOWED=YES COMPILER_INDEX_STORE_ENABLE=NO CC=clang CPLUSPLUS=clang++ LD=clang LDPLUSPLUS=clang++ IPHONEOS_DEPLOYMENT_TARGET=13.0 TVOS_DEPLOYMENT_TARGET=13.0", 
+                              universal_newlines=True, 
+                              shell=True, 
+                              stdout=subprocess.PIPE)
+    logging.info("------------")
+    build_info = result.stdout.read()
+    logging.info(build_info)
+
+    # derived_data_location = os.path.expanduser("~/Library/Developer/Xcode/DerivedData/")
+    for file_dir, _, file_names in os.walk(derived_data_location):
+      for file_name in file_names:
+        if file_name == objc_header:
+          file_path = os.path.join(file_dir, file_name)
+          logging.info(file_path)
+          subprocess.Popen(f"cp {file_path} {os.path.join(output_dir, file_name)}", 
+                                    universal_newlines=True, 
+                                    shell=True, 
+                                    stdout=subprocess.PIPE)
+          result = subprocess.Popen(f"sourcekitten doc --objc {file_path} -- -x objective-c -isysroot $(xcrun --show-sdk-path) -I $(pwd)", 
+                                    universal_newlines=True, 
+                                    shell=True, 
+                                    stdout=subprocess.PIPE)
+          logging.info("------------")
+          api_info = result.stdout.read()
+          output_path = os.path.join(output_dir, file_name + ".json")
+          logging.info(output_path)
+          with open(output_path, 'w') as f:
+            f.write(api_info)
+
+
+def parse_cmdline_args():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('-f', '--file_list', nargs='+', default=[])
+  parser.add_argument('-o', '--output_dir', default="")
+
+  args = parser.parse_args()
+  return args
+
+
+if __name__ == '__main__':
+  main()
\ No newline at end of file