firebase

Firebase JavaScript SDK

The Firebase JavaScript SDK implements the client-side libraries used by applications using Firebase services. This SDK is distributed via:

• CDN
• npm package

To get started using Firebase, see Add Firebase to your JavaScript Project.

Upgrade to Version 9

Version 9 has a redesigned API that supports tree-shaking. Read the Upgrade Guide to learn more.

Supported Environments

Please see Environment Support.

SDK Dev Workflow

Prerequisites

Node.js

Before you can start working on the Firebase JS SDK, you need to have Node.js installed on your machine. As of July 17th, 2026 the team has been testing with Node.js version 20.19.0, but the required version of Node.js may change as we update our dependencies.

To download Node.js visit https://nodejs.org/en/download/.

NOTE: You can use a tool like NVM or N to install and manage multiple node versions

Yarn

In addition to Node.js we use yarn to facilitate multi package development.

To install yarn follow the instructions listed on their website: https://yarnpkg.com/en/docs/install

This repo currently supports building with yarn 1.x. For instance, after installing yarn, run

$ yarn set version 1.22.11

Java

The closure compiler requires a modern Java installation. Java 11+ should be installed: https://www.oracle.com/java/technologies/downloads/#java11

Verify Prerequisites

You can verify your setup by running the following commands in your terminal:

$ node -v
$ yarn -v
$ java -version

Your node version should be 20.19.0 or greater, your yarn version should be between 1.0.0 and 1.22.11, and your java version should be 11.0 or greater.

NOTE: We will update the documentation as new versions are required, however for continuing development on the SDK, staying up to date on the stable versions of these packages is advised

Install Dependencies

Once you have Node.js and yarn installed on your machine and have validated that you are running the proper version, you can set up the development environment by running the following at the root of the SDK:

$ yarn

Once you have installed all the dependencies, you can build the entire SDK by running the following command the root of the SDK:

$ yarn build

Testing the SDK

Test Setup

A production project is required to test the Firebase JS SDK. You can create a new project by visiting the Firebase Console.

Web App Setup

Visit the "Project Overview" and select "Add app" under your project name. Register the app with a nickname and click through the remaining steps. Without performing this step, you will encounter the error in the test setup:

FirebaseError: There are no WEB apps associated with this Firebase project

Firestore Database Setup

Visit the "Firestore Database" section of the console and create a Cloud Firestore database. When prompted to select the set of initial security rules, select any option (e.g. "Start in Production Mode") since these permission settings will be overwritten below.

Realtime Database Setup

Visit the "Realtime Database" section of the console and create a realtime database. When prompted to select the set of initial security rules, select any option (e.g. "Start in Locked Mode") since these permission settings will be overwritten below.

Storage Setup

Visit the "Storage" section of the console and create a storage bucket. In order to run the tests, you will need to update your bucket's CORS rules.

1. Create a new file called cors.json with the contents:

[
    {
        "origin": ["http://localhost:8089"],
        "method": ["GET"],
        "maxAgeSeconds": 3600
    }
]

1. Install gsutil from https://cloud.google.com/storage/docs/gsutil_install
2. You will need to login if this is your first time using gsutil. Run gcloud auth login and follow the instructions to login.
3. Run gcloud storage buckets update gs://<your-cloud-storage-bucket> --cors-file=cors.json

For more information, visit https://firebase.google.com/docs/storage/web/download-files#cors_configuration

Then, make sure you have anonymous sign-in provider enabled:

Authentication Support

Visit the authentication config in your project and enable the Anonymous sign-in provider to complete your project config.

Automated Setup

The tests need to be configured to use the Firebase production project that you created in the "Test Setup" section above. To do this, run the yarn test:setup command, as follows:

# Select the Firebase project via the text-based UI. This will run tools/config.js
# and deploy from config/ to your Firebase project.
$ yarn test:setup

# Specify the Firebase project via the command-line arguments.
$ yarn test:setup --projectId=<test_firebase_project_id>

If you see an error like

HTTP Error: 404, Project '<test_firebase_project_id>' does not exist.

then make sure that you have created the database as specified in the "Firestore Database Setup" section above.

Running the tests

Each of the directories in the integration directory as well as the packages directory have their own test suites. You will need to build the SDK before running tests. Test suites can be run all together by running the following command at the root of the package:

$ yarn test

In addition, you can run any of the tests individually by running yarn test in an individual package directory.

Building the SDK

Introduction

The Firebase JS SDK is built with a series of individual packages that are all contained in this repository. Development is coordinated via yarn workspaces and Lerna (a monorepo management tool).

Each package in the packages directory, constitute a piece of our implementation. The SDK is built via a combination of all of these packages which are published under the firebase scope on NPM.

Testing the SDK Locally

Please be sure your product's package has been built before proceeding any further. (If you haven't built this repo before, make sure to run yarn build at the root) In order to manually test your SDK changes locally, you must use yarn link:

$ cd packages/firebase
$ yarn link # initialize the linking to the other folder
$ cd ../<my-product> # Example: $ cd ../firestore
$ yarn link # link your product to make it available elsewhere
$ cd <my-test-app-dir> # cd into your personal project directory
$ yarn link firebase @firebase/<my-product> # tell yarn to use the locally built firebase SDK instead

This will create a symlink and point your <my-test-app-dir> to the locally built version of the firebase SDK.

Helper Scripts

Each package in the packages directory exposes a dev script. This script will set up a watcher for development on the individual piece of the SDK. In addition, there is a top level dev script that can be run to start all of the watch tasks as well as a sandbox server.

You can run the dev script by running the following at the root of the package:

$ yarn dev

Prepush Hooks

As part of this repo, we use the NPM package husky to implement git hooks. We leverage the prepush hook to do two things:

• Automated code styling (using prettier)
• Automated LICENSE header insertion

Contributing

See Contributing for more information on contributing to the Firebase JavaScript SDK.