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:
To install the Emulator Suite:
- 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
- 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
- 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 emulatorsor by editingfirebase.jsonmanually. - Change the path to Security Rules definitions by editing
firebase.jsonmanually.
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.
| Command | Description |
|---|---|
| init emulators | Start an emulator initialization wizard. Identify emulators to be installed and optionally specify emulator port settings. init emulators is non-destructive; accepting defaults will preserve the current emulator configuration. |
Port configuration
Each emulator binds to a different port on your machine with a preferred default value.
| Emulator | Default Port |
|---|---|
| Authentication | 9099 |
| Emulator Suite UI | 4000 |
| Cloud Functions | 5001 |
| Eventarc | 9299 |
| Realtime Database | 9000 |
| Cloud Firestore | 8080 |
| Cloud Storage for Firebase | 9199 |
| Firebase Hosting | 5000 |
| Pub/Sub | 8085 |
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 initorfirebase use. To view the list of projects (and see which one is selected) usefirebase projects:list. - Rules unit tests. The project ID is often specified in calls to the Rules
Unit Testing library methods
initializeTestEnvironmentorinitializeTestApp. - The command line
--projectflag. Passing the Firebase CLI--projectflag 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.
| Command | Description | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| emulators:start | Start emulators for the Firebase products configured in firebase.json.
Emulator processes will continue running until explicitly stopped. Calling
emulators:start will download the emulators to ~/.cache/firebase/emulators/ if
they are not already installed.
|
||||||||||||
| emulators:exec scriptpath | Run the script at scriptpath after starting emulators for the Firebase products
configured in firebase.json. Emulator processes will automatically stop when the
script has finished running.
|
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.
| emulators:export export_directory |
Authentication, Cloud Firestore, Realtime Database or Cloud Storage for Firebase emulator.
Export data from a running Cloud Firestore, Realtime Database or Cloud Storage for Firebase
emulator instance. The specified
You can instruct the emulators to export data automatically when they shutdown using the
|
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.jsonfile in your repository, you must add a command line argument to theemulators:startoremulators:execcommand 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
| Android | Apple platforms | Web |
Firebase UI Android |
Firebase UI iOS |
Firebase UI Web |
|
|---|---|---|---|---|---|---|
| Realtime Database | 19.4.0 | 7.2.0 | 8.0.0 | 6.4.0 | Future | N/A |
| Cloud Firestore | 21.6.0 | 7.2.0 | 8.0.0 | 6.4.0 | Future | N/A |
| Authentication | 20.0.0 | 7.0.0 | 8.0.0 | 7.0.0 | Future | 4.7.2 |
| Cloud Storage for Firebase | 20.0.0 | 8.0.0 | 8.4.0 | 7.0.0 | 11.0.0 | N/A |
| Cloud Functions | 19.1.0 | 7.2.0 | 8.0.0 | N/A | N/A | N/A |
| Hosting | N/A | N/A | N/A | N/A | N/A | N/A |
| Extensions | N/A | N/A | N/A | N/A | N/A | N/A |
Admin SDK availability
| Node | Java | Python | Go | |
|---|---|---|---|---|
| Realtime Database | 8.6.0 | 6.10.0 | 2.18.0 | Future |
| Cloud Firestore | 8.0.0 | 6.10.0 | 3.0.0 | 1.0.0 |
| Authentication | 9.3.0 | 7.2.0 | 5.0.0 | 4.2.0 |
| Cloud Storage for Firebase | 9.8.0 | Future | Future | Future |
| Cloud Functions | N/A | N/A | N/A | N/A |
| Hosting | N/A | N/A | N/A | N/A |
| Extensions | N/A | N/A | N/A | N/A |