diff --git a/.changeset/mighty-insects-judge.md b/.changeset/mighty-insects-judge.md
new file mode 100644
index 00000000000..701e3b28e27
--- /dev/null
+++ b/.changeset/mighty-insects-judge.md
@@ -0,0 +1,13 @@
+---
+'@firebase/app': minor
+'@firebase/app-types': minor
+'@firebase/util': minor
+'@firebase/auth': patch
+'@firebase/database': patch
+'@firebase/firestore': patch
+'@firebase/functions': patch
+'@firebase/storage': patch
+'firebase': minor
+---
+
+Add functionality to auto-initialize project config and emulator settings from global defaults provided by framework tooling.
diff --git a/common/api-review/app.api.md b/common/api-review/app.api.md
index 8d35bc4096f..52f134dac16 100644
--- a/common/api-review/app.api.md
+++ b/common/api-review/app.api.md
@@ -93,6 +93,9 @@ export function initializeApp(options: FirebaseOptions, name?: string): Firebase
 // @public
 export function initializeApp(options: FirebaseOptions, config?: FirebaseAppSettings): FirebaseApp;
 
+// @public
+export function initializeApp(): FirebaseApp;
+
 // @public
 export function onLog(logCallback: LogCallback | null, options?: LogOptions): void;
 
diff --git a/common/api-review/firestore.api.md b/common/api-review/firestore.api.md
index 3b6538d867b..e3a60e64129 100644
--- a/common/api-review/firestore.api.md
+++ b/common/api-review/firestore.api.md
@@ -228,10 +228,10 @@ export function getDocsFromCache<T>(query: Query<T>): Promise<QuerySnapshot<T>>;
 export function getDocsFromServer<T>(query: Query<T>): Promise<QuerySnapshot<T>>;
 
 // @public
-export function getFirestore(): Firestore;
+export function getFirestore(app: FirebaseApp): Firestore;
 
 // @public
-export function getFirestore(app: FirebaseApp): Firestore;
+export function getFirestore(): Firestore;
 
 // @public
 export function increment(n: number): FieldValue;
diff --git a/common/api-review/util.api.md b/common/api-review/util.api.md
index 25657980b0e..57e18bd3d2b 100644
--- a/common/api-review/util.api.md
+++ b/common/api-review/util.api.md
@@ -173,11 +173,28 @@ export function errorPrefix(fnName: string, argName: string): string;
 // @public (undocumented)
 export type Executor<T> = (observer: Observer<T>) => void;
 
+// @public
+export type ExperimentalKey = 'authTokenSyncURL' | 'authIdTokenMaxAge';
+
 // Warning: (ae-missing-release-tag) "extractQuerystring" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public
 export function extractQuerystring(url: string): string;
 
+// @public
+export interface FirebaseDefaults {
+    // (undocumented)
+    [key: string]: unknown;
+    // (undocumented)
+    _authIdTokenMaxAge?: number;
+    // (undocumented)
+    _authTokenSyncURL?: string;
+    // (undocumented)
+    config?: Record<string, string>;
+    // (undocumented)
+    emulatorHosts?: Record<string, string>;
+}
+
 // Warning: (ae-missing-release-tag) "FirebaseError" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public (undocumented)
@@ -195,6 +212,15 @@ export class FirebaseError extends Error {
 // @public
 export type FirebaseSignInProvider = 'custom' | 'email' | 'password' | 'phone' | 'anonymous' | 'google.com' | 'facebook.com' | 'github.com' | 'twitter.com' | 'microsoft.com' | 'apple.com';
 
+// @public
+export const getDefaultAppConfig: () => Record<string, string> | undefined;
+
+// @public
+export const getDefaultEmulatorHost: (productName: string) => string | undefined;
+
+// @public
+export const getExperimentalSetting: <T extends ExperimentalKey>(name: T) => FirebaseDefaults[`_${T}`];
+
 // Warning: (ae-missing-release-tag) "getGlobal" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public
diff --git a/packages/app/src/api.ts b/packages/app/src/api.ts
index 1a713b242c1..b76a00e2d1b 100644
--- a/packages/app/src/api.ts
+++ b/packages/app/src/api.ts
@@ -39,7 +39,7 @@ import {
   LogOptions,
   setUserLogHandler
 } from '@firebase/logger';
-import { deepEqual } from '@firebase/util';
+import { deepEqual, getDefaultAppConfig } from '@firebase/util';
 
 export { FirebaseError } from '@firebase/util';
 
@@ -110,10 +110,18 @@ export function initializeApp(
   options: FirebaseOptions,
   config?: FirebaseAppSettings
 ): FirebaseApp;
+/**
+ * Creates and initializes a FirebaseApp instance.
+ *
+ * @public
+ */
+export function initializeApp(): FirebaseApp;
 export function initializeApp(
-  options: FirebaseOptions,
+  _options?: FirebaseOptions,
   rawConfig = {}
 ): FirebaseApp {
+  let options = _options;
+
   if (typeof rawConfig !== 'object') {
     const name = rawConfig;
     rawConfig = { name };
@@ -132,6 +140,12 @@ export function initializeApp(
     });
   }
 
+  options ||= getDefaultAppConfig();
+
+  if (!options) {
+    throw ERROR_FACTORY.create(AppError.NO_OPTIONS);
+  }
+
   const existingApp = _apps.get(name) as FirebaseAppImpl;
   if (existingApp) {
     // return the existing app if options and config deep equal the ones in the existing app.
@@ -188,6 +202,9 @@ export function initializeApp(
  */
 export function getApp(name: string = DEFAULT_ENTRY_NAME): FirebaseApp {
   const app = _apps.get(name);
+  if (!app && name === DEFAULT_ENTRY_NAME) {
+    return initializeApp();
+  }
   if (!app) {
     throw ERROR_FACTORY.create(AppError.NO_APP, { appName: name });
   }
diff --git a/packages/app/src/errors.ts b/packages/app/src/errors.ts
index ed307085b09..6cd50e90942 100644
--- a/packages/app/src/errors.ts
+++ b/packages/app/src/errors.ts
@@ -22,6 +22,7 @@ export const enum AppError {
   BAD_APP_NAME = 'bad-app-name',
   DUPLICATE_APP = 'duplicate-app',
   APP_DELETED = 'app-deleted',
+  NO_OPTIONS = 'no-options',
   INVALID_APP_ARGUMENT = 'invalid-app-argument',
   INVALID_LOG_ARGUMENT = 'invalid-log-argument',
   IDB_OPEN = 'idb-open',
@@ -38,6 +39,8 @@ const ERRORS: ErrorMap<AppError> = {
   [AppError.DUPLICATE_APP]:
     "Firebase App named '{$appName}' already exists with different options or config",
   [AppError.APP_DELETED]: "Firebase App named '{$appName}' already deleted",
+  [AppError.NO_OPTIONS]:
+    'Need to provide options, when not being deployed to hosting via source.',
   [AppError.INVALID_APP_ARGUMENT]:
     'firebase.{$appName}() takes either no argument or a ' +
     'Firebase App instance.',
diff --git a/packages/auth/src/platform_browser/index.ts b/packages/auth/src/platform_browser/index.ts
index 3d206c3706d..9bfe4e3b01a 100644
--- a/packages/auth/src/platform_browser/index.ts
+++ b/packages/auth/src/platform_browser/index.ts
@@ -17,14 +17,50 @@
 
 import { FirebaseApp, getApp, _getProvider } from '@firebase/app';
 
-import { initializeAuth } from '..';
+import {
+  initializeAuth,
+  beforeAuthStateChanged,
+  onIdTokenChanged,
+  connectAuthEmulator
+} from '..';
 import { registerAuth } from '../core/auth/register';
 import { ClientPlatform } from '../core/util/version';
 import { browserLocalPersistence } from './persistence/local_storage';
 import { browserSessionPersistence } from './persistence/session_storage';
 import { indexedDBLocalPersistence } from './persistence/indexed_db';
 import { browserPopupRedirectResolver } from './popup_redirect';
-import { Auth } from '../model/public_types';
+import { Auth, User } from '../model/public_types';
+import { getDefaultEmulatorHost, getExperimentalSetting } from '@firebase/util';
+
+const DEFAULT_ID_TOKEN_MAX_AGE = 5 * 60;
+const authIdTokenMaxAge =
+  getExperimentalSetting('authIdTokenMaxAge') || DEFAULT_ID_TOKEN_MAX_AGE;
+
+let lastPostedIdToken: string | undefined | null = null;
+
+const mintCookieFactory = (url: string) => async (user: User | null) => {
+  const idTokenResult = user && (await user.getIdTokenResult());
+  const idTokenAge =
+    idTokenResult &&
+    (new Date().getTime() - Date.parse(idTokenResult.issuedAtTime)) / 1_000;
+  if (idTokenAge && idTokenAge > authIdTokenMaxAge) {
+    return;
+  }
+  // Specifically trip null => undefined when logged out, to delete any existing cookie
+  const idToken = idTokenResult?.token;
+  if (lastPostedIdToken === idToken) {
+    return;
+  }
+  lastPostedIdToken = idToken;
+  await fetch(url, {
+    method: idToken ? 'POST' : 'DELETE',
+    headers: idToken
+      ? {
+          'Authorization': `Bearer ${idToken}`
+        }
+      : {}
+  });
+};
 
 /**
  * Returns the Auth instance associated with the provided {@link @firebase/app#FirebaseApp}.
@@ -41,7 +77,7 @@ export function getAuth(app: FirebaseApp = getApp()): Auth {
     return provider.getImmediate();
   }
 
-  return initializeAuth(app, {
+  const auth = initializeAuth(app, {
     popupRedirectResolver: browserPopupRedirectResolver,
     persistence: [
       indexedDBLocalPersistence,
@@ -49,6 +85,22 @@ export function getAuth(app: FirebaseApp = getApp()): Auth {
       browserSessionPersistence
     ]
   });
+
+  const authTokenSyncUrl = getExperimentalSetting('authTokenSyncURL');
+  if (authTokenSyncUrl) {
+    const mintCookie = mintCookieFactory(authTokenSyncUrl);
+    beforeAuthStateChanged(auth, mintCookie, () =>
+      mintCookie(auth.currentUser)
+    );
+    onIdTokenChanged(auth, user => mintCookie(user));
+  }
+
+  const authEmulatorHost = getDefaultEmulatorHost('auth');
+  if (authEmulatorHost) {
+    connectAuthEmulator(auth, `http://${authEmulatorHost}`);
+  }
+
+  return auth;
 }
 
 registerAuth(ClientPlatform.BROWSER);
diff --git a/packages/auth/src/platform_node/index.ts b/packages/auth/src/platform_node/index.ts
index 14f5a531b93..570f1e0589f 100644
--- a/packages/auth/src/platform_node/index.ts
+++ b/packages/auth/src/platform_node/index.ts
@@ -21,13 +21,14 @@ import { _createError } from '../core/util/assert';
 import { FirebaseApp, getApp, _getProvider } from '@firebase/app';
 import { Auth } from '../model/public_types';
 
-import { initializeAuth, inMemoryPersistence } from '..';
+import { initializeAuth, inMemoryPersistence, connectAuthEmulator } from '..';
 import { registerAuth } from '../core/auth/register';
 import { ClientPlatform } from '../core/util/version';
 import { AuthImpl } from '../core/auth/auth_impl';
 
 import { FetchProvider } from '../core/util/fetch_provider';
 import * as fetchImpl from 'node-fetch';
+import { getDefaultEmulatorHost } from '@firebase/util';
 
 // Initialize the fetch polyfill, the types are slightly off so just cast and hope for the best
 FetchProvider.initialize(
@@ -46,7 +47,14 @@ export function getAuth(app: FirebaseApp = getApp()): Auth {
     return provider.getImmediate();
   }
 
-  return initializeAuth(app);
+  const auth = initializeAuth(app);
+
+  const authEmulatorHost = getDefaultEmulatorHost('auth');
+  if (authEmulatorHost) {
+    connectAuthEmulator(auth, `http://${authEmulatorHost}`);
+  }
+
+  return auth;
 }
 
 registerAuth(ClientPlatform.NODE);
diff --git a/packages/database/src/api/Database.ts b/packages/database/src/api/Database.ts
index 840e1be5aff..db0273b1721 100644
--- a/packages/database/src/api/Database.ts
+++ b/packages/database/src/api/Database.ts
@@ -27,7 +27,8 @@ import { Provider } from '@firebase/component';
 import {
   getModularInstance,
   createMockUserToken,
-  EmulatorMockTokenOptions
+  EmulatorMockTokenOptions,
+  getDefaultEmulatorHost
 } from '@firebase/util';
 
 import { AppCheckTokenProvider } from '../core/AppCheckTokenProvider';
@@ -316,9 +317,15 @@ export function getDatabase(
   app: FirebaseApp = getApp(),
   url?: string
 ): Database {
-  return _getProvider(app, 'database').getImmediate({
+  const db = _getProvider(app, 'database').getImmediate({
     identifier: url
   }) as Database;
+  const databaseEmulatorHost = getDefaultEmulatorHost('database');
+  if (databaseEmulatorHost) {
+    const [host, port] = databaseEmulatorHost.split(':');
+    connectDatabaseEmulator(db, host, parseInt(port, 10));
+  }
+  return db;
 }
 
 /**
diff --git a/packages/firestore/externs.json b/packages/firestore/externs.json
index a4c36074978..fcd6408548c 100644
--- a/packages/firestore/externs.json
+++ b/packages/firestore/externs.json
@@ -26,6 +26,7 @@
     "packages/logger/dist/src/logger.d.ts",
     "packages/webchannel-wrapper/src/index.d.ts",
     "packages/util/dist/src/crypt.d.ts",
+    "packages/util/dist/src/defaults.d.ts",
     "packages/util/dist/src/emulator.d.ts",
     "packages/util/dist/src/environment.d.ts",
     "packages/util/dist/src/compat.d.ts",
diff --git a/packages/firestore/src/api/database.ts b/packages/firestore/src/api/database.ts
index 6dbd4463cb3..d61b1ffe21a 100644
--- a/packages/firestore/src/api/database.ts
+++ b/packages/firestore/src/api/database.ts
@@ -15,14 +15,13 @@
  * limitations under the License.
  */
 
-// eslint-disable-next-line import/no-extraneous-dependencies
 import {
   _getProvider,
   _removeServiceInstance,
   FirebaseApp,
   getApp
 } from '@firebase/app';
-import { deepEqual } from '@firebase/util';
+import { deepEqual, getDefaultEmulatorHost } from '@firebase/util';
 
 import { User } from '../auth/user';
 import {
@@ -43,7 +42,10 @@ import {
   setOnlineComponentProvider
 } from '../core/firestore_client';
 import { makeDatabaseInfo } from '../lite-api/components';
-import { Firestore as LiteFirestore } from '../lite-api/database';
+import {
+  Firestore as LiteFirestore,
+  connectFirestoreEmulator
+} from '../lite-api/database';
 import { Query } from '../lite-api/reference';
 import {
   indexedDbClearPersistence,
@@ -186,14 +188,6 @@ export function initializeFirestore(
   });
 }
 
-/**
- * Returns the existing default {@link Firestore} instance that is associated with the
- * default {@link @firebase/app#FirebaseApp}. If no instance exists, initializes a new
- * instance with default settings.
- *
- * @returns The {@link Firestore} instance of the provided app.
- */
-export function getFirestore(): Firestore;
 /**
  * Returns the existing default {@link Firestore} instance that is associated with the
  * provided {@link @firebase/app#FirebaseApp}. If no instance exists, initializes a new
@@ -215,7 +209,15 @@ export function getFirestore(app: FirebaseApp): Firestore;
  */
 export function getFirestore(databaseId: string): Firestore;
 /**
- * Returns the existing {@link Firestore} instance that is associated with the
+ * Returns the existing default {@link Firestore} instance that is associated with the
+ * default {@link @firebase/app#FirebaseApp}. If no instance exists, initializes a new
+ * instance with default settings.
+ *
+ * @returns The {@link Firestore} instance of the provided app.
+ */
+export function getFirestore(): Firestore;
+/**
+ * Returns the existing default {@link Firestore} instance that is associated with the
  * provided {@link @firebase/app#FirebaseApp}. If no instance exists, initializes a new
  * instance with default settings.
  *
@@ -236,9 +238,17 @@ export function getFirestore(
     typeof appOrDatabaseId === 'string'
       ? appOrDatabaseId
       : optionalDatabaseId || DEFAULT_DATABASE_NAME;
-  return _getProvider(app, 'firestore').getImmediate({
+  const db = _getProvider(app, 'firestore').getImmediate({
     identifier: databaseId
   }) as Firestore;
+  if (!db._initialized) {
+    const firestoreEmulatorHost = getDefaultEmulatorHost('firestore');
+    if (firestoreEmulatorHost) {
+      const [host, port] = firestoreEmulatorHost.split(':');
+      connectFirestoreEmulator(db, host, parseInt(port, 10));
+    }
+  }
+  return db;
 }
 
 /**
diff --git a/packages/firestore/src/lite-api/database.ts b/packages/firestore/src/lite-api/database.ts
index c7ab4d5b437..dc6d509a6b5 100644
--- a/packages/firestore/src/lite-api/database.ts
+++ b/packages/firestore/src/lite-api/database.ts
@@ -22,7 +22,11 @@ import {
   FirebaseApp,
   getApp
 } from '@firebase/app';
-import { createMockUserToken, EmulatorMockTokenOptions } from '@firebase/util';
+import {
+  createMockUserToken,
+  EmulatorMockTokenOptions,
+  getDefaultEmulatorHost
+} from '@firebase/util';
 
 import {
   CredentialsProvider,
@@ -44,6 +48,8 @@ import {
   FirestoreSettings
 } from './settings';
 
+export { EmulatorMockTokenOptions } from '@firebase/util';
+
 declare module '@firebase/component' {
   interface NameServiceMapping {
     'firestore/lite': Firestore;
@@ -260,12 +266,19 @@ export function getFirestore(
     typeof appOrDatabaseId === 'string'
       ? appOrDatabaseId
       : optionalDatabaseId || '(default)';
-  return _getProvider(app, 'firestore/lite').getImmediate({
+  const db = _getProvider(app, 'firestore/lite').getImmediate({
     identifier: databaseId
   }) as Firestore;
+  if (!db._initialized) {
+    const firestoreEmulatorHost = getDefaultEmulatorHost('firestore');
+    if (firestoreEmulatorHost) {
+      const [host, port] = firestoreEmulatorHost.split(':');
+      connectFirestoreEmulator(db, host, parseInt(port, 10));
+    }
+  }
+  return db;
 }
 
-export { EmulatorMockTokenOptions } from '@firebase/util';
 /**
  * Modify this instance to communicate with the Cloud Firestore emulator.
  *
diff --git a/packages/functions/src/api.ts b/packages/functions/src/api.ts
index 52913263041..f6b5066b9a8 100644
--- a/packages/functions/src/api.ts
+++ b/packages/functions/src/api.ts
@@ -27,7 +27,7 @@ import {
   httpsCallable as _httpsCallable,
   httpsCallableFromURL as _httpsCallableFromURL
 } from './service';
-import { getModularInstance } from '@firebase/util';
+import { getModularInstance, getDefaultEmulatorHost } from '@firebase/util';
 
 export * from './public-types';
 
@@ -51,6 +51,12 @@ export function getFunctions(
   const functionsInstance = functionsProvider.getImmediate({
     identifier: regionOrCustomDomain
   });
+  const functionsEmulatorHost = getDefaultEmulatorHost('functions');
+  if (functionsEmulatorHost) {
+    const [host, port] = functionsEmulatorHost.split(':');
+    // eslint-disable-next-line no-restricted-globals
+    connectFunctionsEmulator(functionsInstance, host, parseInt(port, 10));
+  }
   return functionsInstance;
 }
 
diff --git a/packages/storage/src/api.ts b/packages/storage/src/api.ts
index a489cacccb8..4b59c310543 100644
--- a/packages/storage/src/api.ts
+++ b/packages/storage/src/api.ts
@@ -14,7 +14,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-// eslint-disable-next-line import/no-extraneous-dependencies
 import { _getProvider, FirebaseApp, getApp } from '@firebase/app';
 
 import {
@@ -51,7 +50,11 @@ import {
   getBytesInternal
 } from './reference';
 import { STORAGE_TYPE } from './constants';
-import { EmulatorMockTokenOptions, getModularInstance } from '@firebase/util';
+import {
+  EmulatorMockTokenOptions,
+  getModularInstance,
+  getDefaultEmulatorHost
+} from '@firebase/util';
 import { StringFormat } from './implementation/string';
 
 export { EmulatorMockTokenOptions } from '@firebase/util';
@@ -331,6 +334,12 @@ export function getStorage(
   const storageInstance = storageProvider.getImmediate({
     identifier: bucketUrl
   });
+  const storageEmulatorHost = getDefaultEmulatorHost('storage');
+  if (storageEmulatorHost) {
+    const [host, port] = storageEmulatorHost.split(':');
+    // eslint-disable-next-line no-restricted-globals
+    connectStorageEmulator(storageInstance, host, parseInt(port, 10));
+  }
   return storageInstance;
 }
 
diff --git a/packages/util/index.node.ts b/packages/util/index.node.ts
index d39d5253c1f..d63584284ac 100644
--- a/packages/util/index.node.ts
+++ b/packages/util/index.node.ts
@@ -24,6 +24,7 @@ export * from './src/assert';
 export * from './src/crypt';
 export * from './src/constants';
 export * from './src/deepCopy';
+export * from './src/defaults';
 export * from './src/deferred';
 export * from './src/emulator';
 export * from './src/environment';
diff --git a/packages/util/index.ts b/packages/util/index.ts
index 3f38c307eb3..c529580b24e 100644
--- a/packages/util/index.ts
+++ b/packages/util/index.ts
@@ -19,6 +19,7 @@ export * from './src/assert';
 export * from './src/crypt';
 export * from './src/constants';
 export * from './src/deepCopy';
+export * from './src/defaults';
 export * from './src/deferred';
 export * from './src/emulator';
 export * from './src/environment';
diff --git a/packages/util/src/defaults.ts b/packages/util/src/defaults.ts
new file mode 100644
index 00000000000..6acc5886b5c
--- /dev/null
+++ b/packages/util/src/defaults.ts
@@ -0,0 +1,133 @@
+/**
+ * @license
+ * Copyright 2022 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 { base64Decode } from './crypt';
+import { getGlobal } from './environment';
+
+/**
+ * Keys for experimental properties on the `FirebaseDefaults` object.
+ * @public
+ */
+export type ExperimentalKey = 'authTokenSyncURL' | 'authIdTokenMaxAge';
+
+/**
+ * An object that can be injected into the environment as __FIREBASE_DEFAULTS__,
+ * either as a property of globalThis, a shell environment variable, or a
+ * cookie.
+ *
+ * This object can be used to automatically configure and initialize
+ * a Firebase app as well as any emulators.
+ *
+ * @public
+ */
+export interface FirebaseDefaults {
+  config?: Record<string, string>;
+  emulatorHosts?: Record<string, string>;
+  _authTokenSyncURL?: string;
+  _authIdTokenMaxAge?: number;
+  [key: string]: unknown;
+}
+
+declare global {
+  // Need `var` for this to work.
+  // eslint-disable-next-line no-var
+  var __FIREBASE_DEFAULTS__: FirebaseDefaults | undefined;
+}
+
+const getDefaultsFromGlobal = (): FirebaseDefaults | undefined =>
+  getGlobal().__FIREBASE_DEFAULTS__;
+
+/**
+ * Attempt to read defaults from a JSON string provided to
+ * process.env.__FIREBASE_DEFAULTS__ or a JSON file whose path is in
+ * process.env.__FIREBASE_DEFAULTS_PATH__
+ */
+const getDefaultsFromEnvVariable = (): FirebaseDefaults | undefined => {
+  if (typeof process === 'undefined') {
+    return;
+  }
+  const defaultsJsonString = process.env.__FIREBASE_DEFAULTS__;
+  const defaultsJsonPath = process.env.__FIREBASE_DEFAULTS_PATH__;
+  if (defaultsJsonString) {
+    if (defaultsJsonPath) {
+      console.warn(
+        `Values were provided for both __FIREBASE_DEFAULTS__ ` +
+          `and __FIREBASE_DEFAULTS_PATH__. __FIREBASE_DEFAULTS_PATH__ ` +
+          `will be ignored.`
+      );
+    }
+    return JSON.parse(defaultsJsonString);
+  }
+  if (defaultsJsonPath && typeof require !== 'undefined') {
+    try {
+      // eslint-disable-next-line @typescript-eslint/no-require-imports
+      const json = require(defaultsJsonPath);
+      return json;
+    } catch (e) {
+      console.warn(
+        `Unable to read defaults from file provided to ` +
+          `__FIREBASE_DEFAULTS_PATH__: ${defaultsJsonPath}`
+      );
+    }
+  }
+};
+
+const getDefaultsFromCookie = (): FirebaseDefaults | undefined => {
+  if (typeof document === 'undefined') {
+    return;
+  }
+  const match = document.cookie.match(/__FIREBASE_DEFAULTS__=([^;]+)/);
+  const decoded = match && base64Decode(match[1]);
+  return decoded && JSON.parse(decoded);
+};
+
+/**
+ * Get the __FIREBASE_DEFAULTS__ object. It checks in order:
+ * (1) if such an object exists as a property of `globalThis`
+ * (2) if such an object was provided on a shell environment variable
+ * (3) if such an object exists in a cookie
+ */
+const getDefaults = (): FirebaseDefaults | undefined =>
+  getDefaultsFromGlobal() ||
+  getDefaultsFromEnvVariable() ||
+  getDefaultsFromCookie();
+
+/**
+ * Returns emulator host stored in the __FIREBASE_DEFAULTS__ object
+ * for the given product.
+ * @public
+ */
+export const getDefaultEmulatorHost = (
+  productName: string
+): string | undefined => getDefaults()?.emulatorHosts?.[productName];
+
+/**
+ * Returns Firebase app config stored in the __FIREBASE_DEFAULTS__ object.
+ * @public
+ */
+export const getDefaultAppConfig = (): Record<string, string> | undefined =>
+  getDefaults()?.config;
+
+/**
+ * Returns an experimental setting on the __FIREBASE_DEFAULTS__ object (properties
+ * prefixed by "_")
+ * @public
+ */
+export const getExperimentalSetting = <T extends ExperimentalKey>(
+  name: T
+): FirebaseDefaults[`_${T}`] =>
+  getDefaults()?.[`_${name}`] as FirebaseDefaults[`_${T}`];