Firebase Core

Dart implementation of the Firebase Core API, which enables connecting to multiple Firebase apps.

Note: This library is still under development, and some APIs might not be available yet or work correctly. Please feel free to open an issue here or even a pull requests if you feel brave.



1. Add this to your package's dependencies and run flutter pub get:

  firebase_core_vm: ^0.0.7

2. Import it

import 'package:firebase_core_vm/firebase_core_vm.dart';

3. Create a Firebase project

If you already have a Firebase project for you mobile/web apps you can skip this step.

4. Initialize the FirebaseApp

FirebaseOptions options;
if (Platform.isLinux) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyD9HeqeXUOXJh_DPDl211x8seUXlNmiJj0',
} else if (Platform.isMacOS) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyBQgB5s3n8WvyCOxhCws-RVf3C-6VnGg0A',
} else if (Platform.isWindows) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyBNeYDWMlalWRL2M2_UhE5kiMmvVf3o9BM',
} else if (Platform.isAndroid) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyAM1bGAY-Bd4onFPFb2dBCJA3kx0eiWnSg',
    applicationId: '1:233259864964:android:b2ec71b130a3170cd583d1',
} else if (Platform.isIOS) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyBguTk4w2Xk2LD0mSdB2Pi9LTtt5BeAE6U',
    applicationId: '1:233259864964:ios:fff621fea008bff1d583d1',
} else if (Platform.isFuchsia) {
  options = const FirebaseOptions(
    apiKey: 'AIzaSyBOPFxmw3fni8Inzb_RhFDjb9zznXHfaRo',


This initializes the default FirebaseApp which can be accessed using FirebaseApp.instance. For platforms that Firebase does not support by default like Windows, Linux, macOS and others, you need to generate a unique applicationId and an apiKey.

Create API Key

  1. Go to the Google Cloud Platform console and select you project
  2. Go to APIs & Service -> Credentials
  3. Create new credentials for your app by selecting CREATE CREDENTIALS and then API Key

Create an Application ID

Since desktop is not an officially supported platform, we need to create applicationId for our local use.

  1. Construct the first part of you applicationId following this pattern <appCount>:<projectNumber>:<os>.
    • appCount - TL;DR set it to 1. The appNumber is an incrementing value that starts at 1 and represents the index of your applications for this platform that uses the same Firebase project.
    • projectNumber - is your project number and can be found on the Google Cloud Platform Dashboard in the Project info card.
    • os - windows, macos, linux, my-custom-os-because-i-can
  2. Generate the SHA1 hash of this part. You can use this tool
  3. Add the SHA1 hash to the first part, so you applicationId looks like this <appNumber>:<gcmSenderID>:<os>:sha1(<appNumber>:<gcmSenderID>:<os>) (eg. 1:233259864964:macos:0bdc69800dd31cde15627229f39a6379865e8be1)

4. Initialize multiple FirebaseApp objects

  1. make sure you first register this package:
    import 'package:firebase_core/firebase_core.dart';
    import 'package:firebase_core_dart/firebase_core_dart.dart';
    import 'package:flutter/material.dart';
    void main() {
      if (isDesktop) {
  2. Use firebase_core to initialize the app you want as you normally would.
      Future<void> _configure() async {
        final FirebaseApp app = await FirebaseApp.configure(
          name: 'foo',
          options: const FirebaseOptions(
            apiKey: 'AIzaSyBQgB5s3n8WvyCOxhCws-RVf3C-6VnGg0A',
            databaseURL: '',
            projectID: 'flutter-sdk',
            storageBucket: '',
            gcmSenderID: '233259864964',
        assert(app != null);
        print('Configured $app');

Note: You can have a look at the example app on how you can initialize use different FirebaseOptions depending on the platform you are on.

Get configuration from Firebase console

  1. projectID you can be found on the Project Settings tab
  2. gcmSenderID/projectNumber you can be found on the Project Settings -> Cloud Messaging -> Sender ID
  3. databaseURL you can find it on the Database tab and it usually looks like this https://<project-id>
  4. storageBucket you can find it on the Storage tab and it usually looks like this <project-id>


Platform dependencies

In order to provide core functionality, Firebase services requires access to different events and services. For example Firebase Auth needs a permanent storage in witch to save the current session, tokens and other information. This helps by not having the user to login every time the app starts. Also Firebase Auth doesn't need to trigger a token refresh if the app is in background. All this events and services are provided to the FirebaseApp by extending the PlatformDependencies class.

The PlatformDependencies class defines the following interface:

  1. onBackgroundChanged is a BehaviorSubject that should emit true when the app goes in background. Default implementations assumes the app never goes in background.

  2. onNetworkConnected is a BehaviorSubject that should emit true when the app have internet connection. Default implementation assumes there is always internet connection.

  3. headersBuilder provides you a way to add headers to firebase services request. This is currently only used by Firebase Auth. Defaults to null.

  4. storage is a simple interface that should allow to persisting key/value pairs. It's your responsibility to make sure the store is safe and survives app restarts. Default implementation uses an in memory storage that does not survives app restarts.

  5. authProvider is used to generate authorization headers. If you plan to use Firebase Auth, the authProvider functionality will be provided by the corresponding FirebaseAuth instance. If Firebase Auth is not used it defaults to null.

All Firebase services can work with the default implementation. However it is a good idea to provide your own based on the application that you are trying to use. You can find a good example here.