Install, configure and integrate Local Emulator Suite

The Firebase Local Emulator Suite can be installed and configured for different prototype and test environments, anything from one-off prototyping sessions to production-scale continuous integration workflows.

Install the Local Emulator Suite

Before installing the Emulator Suite you will need:

• Node.js version 16.0 or higher.
• Java JDK version 11 or higher.

To install the Emulator Suite:

1. Install the Firebase CLI. If you don't already have the Firebase CLI installed, install it now. You will need CLI version 8.14.0 or higher to use the Emulator Suite. You can check which version you have installed using the following command:

   firebase --version

2. If you haven't already done so, initialize the current working directory as a Firebase project, following the onscreen prompts to specify which products to use:

   firebase init

3. Set up the Emulator Suite. This command starts a configuration wizard that lets you select emulators of interest, download the corresponding emulator binary files, and set emulator ports if the defaults are not appropriate.

   firebase init emulators

Once an emulator is installed, no update checks are performed and no additional automatic downloads will occur until you update your Firebase CLI version.

Configure Emulator Suite

You can optionally configure the emulators' network ports and path to Security Rules definitions in the firebase.json file:

• Change emulator ports by running firebase init emulators or by editing firebase.json manually.
• Change the path to Security Rules definitions by editing firebase.json manually.

If you don't configure these settings, the emulators will listen on their default ports, and the Cloud Firestore, Realtime Database and Cloud Storage for Firebase emulators will run with open data security.

Port configuration

Each emulator binds to a different port on your machine with a preferred default value.

Project ID configuration

Depending on how you invoke emulators, you may run multiple instances of an emulator using different Firebase project IDs or multiple emulator instances for a given project ID. In such cases, emulator instances are running in a separate environment.

It's generally a good practice to set one project ID for all emulator invocations, so the Emulator Suite UI, different product emulators, and all running instances of a particular emulator can communicate correctly in all cases.

Local Emulator Suite issues warnings when it detects multiple project IDs in the environment, though you can override this behavior by setting the singleProjectMode key to false in your firebase.json.

You can check project ID declaration(s) for mismatches in:

• The default project in the command line. By default, the project ID will be taken on startup from the project selected with firebase init or firebase use. To view the list of projects (and see which one is selected) use firebase projects:list.
• Rules unit tests. The project ID is often specified in calls to the Rules Unit Testing library methods initializeTestEnvironment or initializeTestApp.
• The command line --project flag. Passing the Firebase CLI --project flag overrides the default project. You'll need to ensure the value of the flag matches the project ID in unit tests and app initialization.

Also check platform-specific project ID configurations you've set while configuring your Apple platforms, Android, and web projects.

Security Rules configuration

The emulators will take Security Rules configuration from the database, firestore and storage configuration keys in firebase.json.

{
  // Existing firebase configuration ...
  "database": {
    "rules": "database.rules.json"
  },
  "firestore": {
    "rules": "firestore.rules"
  },
  "storage": {
    "rules": "storage.rules"
  }

  // ...

  // Optional emulator configuration. Default
  // values are used if absent.
  "emulators": {
    "singleProjectMode": false, // do not warn on detection of multiple project IDs
    "firestore": {
      "port": "8080"
    },
    "ui": {
      "enabled": true,      // Default is `true`
      "port": 4000          // If unspecified, see CLI log for selected port
    },
    "auth": {
      "port": "9099"
    },
    "pubsub": {
      "port": "8085"
    }
  }
}

Specifying Java options

The Realtime Database emulator, Cloud Firestore emulator, and part of Cloud Storage for Firebase emulator are based on Java, which can be customized with JVM flags via the environment variable JAVA_TOOL_OPTIONS.

For example, if you experience Java heap space related errors, you may increase the maximum Java heap size to 4GB:

export JAVA_TOOL_OPTIONS="-Xmx4g"
firebase emulators:start

Multiple flags can be specified in quotes separated by spaces, like JAVA_TOOL_OPTIONS="-Xms2g -Xmx4g". The flags only affect the Java-based components of the emulators and have no effect on other parts of the Firebase CLI, such as Emulator Suite UI.

Start up emulators

You can start emulators to run until manually terminated, or to run for the duration of a designated test script then automatically shut down.

The firebase emulators:exec method is generally more appropriate for continuous integration workflows.

Export and import emulator data

You can export data from the Authentication, Cloud Firestore, Realtime Database and Cloud Storage for Firebase emulators to use as a shareable, common baseline data set. These data sets can be imported using the --import flag, as described above.

Integrate with your CI system

Running containerized Emulator Suite images

Installation and configuration of the Emulator Suite with containers in a typical CI setup is straightforward.

There are a few issues to note:

• JAR files are installed and cached at ~/.cache/firebase/emulators/.

  • You may want to add this path to your CI cache configuration to avoid repeated downloads.

• If you do not have a firebase.json file in your repository, you must add a command line argument to the emulators:start or emulators:exec command to specify which emulators should be started. For example,
  --only functions,firestore.

Generate an auth token (Hosting emulator only)

If your continuous integration workflows rely on Firebase Hosting , then you will need to log in using a token in order to run firebase emulators:exec. The other emulators do not require login.

To generate a token, run firebase login:ci on your local environment; this should not be performed from a CI system. Follow instructions to authenticate. You should only need to perform this step once per project, since the token will be valid across builds. The token should be treated like a password; make sure it is kept secret.

If your CI environment allows you to specify environment variables that can be used in the build scripts, simply create an environment variable called FIREBASE_TOKEN, with the value being the access token string. The Firebase CLI will automatically pick up the FIREBASE_TOKEN environment variable and the emulators will start properly.

As a last resort, you can simply include the token in your build script, but make sure that untrusted parties do not have access. For this hard-coded approach, you can add --token "YOUR_TOKEN_STRING_HERE" to the firebase emulators:exec command.

Use the Emulator Hub REST API

List running emulators

To list the currently running emulators, send a GET request to the /emulators endpoint of the Emulator Hub.

curl localhost:4400/emulators

The result will be a JSON object listing all running emulators and their host/port configuration, for example:

{
  "hub":{
    "name": "hub",
    "host": "localhost",
    "port": 4400
  },
  "functions": {
    "name": "functions",
    "host": "localhost",
    "port": 5001
  }
  "firestore": {
    "name": "firestore",
    "host": "localhost",
    "port": 8080
  }
}

Enable / Disable Background Function Triggers

In some situations you will need to temporarily disable local function and extension triggers. For example you may want to delete all of the data in the Cloud Firestore emulator without triggering any onDelete functions that are running in the Cloud Functions or Extensions emulators.

To temporarily disable local function triggers, send a PUT request to the /functions/disableBackgroundTriggers endpoint of the Emulator Hub.

curl -X PUT localhost:4400/functions/disableBackgroundTriggers

The result will be a JSON object detailing the current state.

{
  "enabled": false
}

To enable local function triggers after they have been disabled, send a PUT request to the /functions/enableBackgroundTriggers endpoint of the Emulator Hub.

curl -X PUT localhost:4400/functions/enableBackgroundTriggers

The result will be a JSON object detailing the current state.

{
  "enabled": true
}

Emulator SDK integrations

The tables in this section indicate which emulators are supported by client and Admin SDKs. Future means emulator support is planned but not yet available.

Client SDK availability

Admin SDK availability