Configure your environment

Often you'll need additional configuration for your functions, such as third-party API keys or tuneable settings. The Firebase SDK for Cloud Functions offers built-in environment configuration to make it easy to store and retrieve this type of data for your project.

Support for Environment Configuration with functions.config() has been removed from Cloud Functions for Firebase v2. functions.config() is replaced by environment variables.

Environment variables

Cloud Functions for Firebase supports the dotenv file format for loading environment variables specified in a .env file to your application runtime. Once deployed, the environment variables can be read via the process.env interface.

To configure your environment this way, create a .env file in your project, add the desired variables, and deploy:

Create a .env file in your functions/ directory:

# Directory layout:
#   my-project/
#     firebase.json
#     functions/
#       .env
#       package.json
#       index.js

Open the .env file for edit, and add the desired keys. For example:
```
PLANET=Earth
AUDIENCE=Humans
```

Deploy functions and verify that environment variables were loaded:

firebase deploy --only functions
# ...
# i functions: Loaded environment variables from .env.
# ...

Once your your custom environment variables are deployed, your function code can access them with process.env syntax:

// Responds with "Hello Earth and Humans"
exports.hello = onRequest((request, response) => {
  response.send(`Hello ${process.env.PLANET} and ${process.env.AUDIENCE}`);
});

Deploying multiple sets of environment variables

If you need an alternative set of environment variables for your Firebase projects (such as staging vs production), create a .env.<project or alias> file and write your project-specific environment variables there. The environment variables from .env and project-specific .env files (if they exist) will be included in all deployed functions.

For example, a project could include these three files containing slightly different values for development and production:

`.env`	`.env.dev`	`.env.prod`
PLANET=Earth AUDIENCE=Humans	AUDIENCE=Dev Humans	AUDIENCE=Prod Humans

Given the values in those separate files, the set of environment variables deployed with your functions will vary depending on your target project:

$ firebase use dev
$ firebase deploy --only functions
i functions: Loaded environment variables from .env, .env.dev.
# Deploys functions with following user-defined environment variables:
#   PLANET=Earth
#   AUDIENCE=Dev Humans

$ firebase use prod
$ firebase deploy --only functions
i functions: Loaded environment variables from .env, .env.prod.
# Deploys functions with following user-defined environment variables:
#   PLANET=Earth
#   AUDIENCE=Prod Humans

Reserved environment variables

Some environment variable keys are reserved for internal use. Do not use any of these keys in your .env files:

All keys starting with X_GOOGLE_
All keys starting EXT_
All keys starting with FIREBASE_
Any key from the following list:
CLOUD_RUNTIME_CONFIG
ENTRY_POINT
GCP_PROJECT
GCLOUD_PROJECT
GOOGLE_CLOUD_PROJECT
FUNCTION_TRIGGER_TYPE
FUNCTION_NAME
FUNCTION_MEMORY_MB
FUNCTION_TIMEOUT_SEC
FUNCTION_IDENTITY
FUNCTION_REGION
FUNCTION_TARGET
FUNCTION_SIGNATURE_TYPE
K_SERVICE
K_REVISION
PORT
K_CONFIGURATION

Store and access sensitive configuration information

Environment variables stored in .env files can be used for function configuration, but you should not consider them a secure way to store sensitive information such as database credentials or API keys. This is especially important if you check your .env files into source control.

To help you store sensitive configuration information, Cloud Functions for Firebase integrates with Google Cloud Secret Manager. This encrypted service stores configuration values securely, while still allowing easy access from your functions when needed.

Create and use a secret

To create a secret, use the Firebase CLI.

To create and use a secret:

From the root of your local project directory, run the following command:
```
firebase functions:secrets:set SECRET_NAME
```
Enter a value for SECRET_NAME.

The CLI echoes a success message and warns that you must deploy functions for the change to take effect.

Before deploying, make sure your functions code allows the function to access the secret using the runWith parameter:

const { onRequest } = require("functions/v2/https");

  exports.processpayment = onRequest(
    { secrets: ["SECRET_NAME"] },
    (data, context) => {
      const myBillingService = initializeBillingService(
        // reference the secret value
        process.env.SECRET_NAME
      );
      // Process the payment
    }
  );

Deploy Cloud Functions:
```
firebase deploy --only functions
```

Now you'll be able to access it like any other environment variable. Conversely, if another function that does not specify the secret in runWith tries to access the secret, it receives an undefined value:

exports.anotherendpoint = onRequest((request, response) => {
  response.send(`The secret API key is ${process.env.SECRET_NAME}`);
  // responds with "The secret API key is undefined" because the `runWith` parameter is missing
});

Once your function is deployed, it will have access to the secret value. Only functions that specifically include a secret in their runWith parameter will have access to that secret as an environment variable. This helps you make sure that secret values are only available where they're needed, reducing the risk of accidentally leaking a secret.

Managing secrets

Use the Firebase CLI to manage your secrets. While managing secrets this way, keep in mind that some CLI changes require you to modify and/or redeploy associated functions. Specifically:

Whenever you set a new value for a secret, you must redeploy all functions that reference that secret for them to pick up the latest value.
If you delete a secret, make sure that none of your deployed functions references that secret. Functions that use a secret value that has been deleted will fail silently.

Here's a summary of the Firebase CLI commands for secret management:

# Change the value of an existing secret
firebase functions:secrets:set SECRET_NAME

# View the value of a secret
functions:secrets:access SECRET_NAME

# Destroy a secret
functions:secrets:destroy SECRET_NAME

# View all secret versions and their state
functions:secrets:get SECRET_NAME

# Automatically clean up all secrets that aren't referenced by any of your functions
functions:secrets:prune

For the access and destroy commands, you can provide the optional version parameter to manage a particular version. For example:

functions:secrets:access SECRET_NAME[@VERSION]

For more information about these operations, pass -h with the command to view CLI help.

How secrets are billed

Secret Manager allows 6 active secret versions at no cost. This means that you can have 6 secrets per month in a Firebase project at no cost.

By default, the Firebase CLI attempts to automatically destroy unused secret versions where appropriate, such as when you deploy functions with a new version of the secret. Also, you can actively clean up unused secrets using functions:secrets:destroy and functions:secrets:prune.

Secret Manager allows 10,000 unbilled monthly access operations on a secret. Function instances read only the secrets specified in their runWith parameter every time they cold start. If you have a lot of function instances reading a lot of secrets, your project may exceed this allowance, at which point you'll be charged $0.03 per 10,000 access operations.

For more information, see Secret Manager Pricing.

Emulator support

Environment configuration with dotenv is designed to interoperate with a local Cloud Functions emulator.

When using a local Cloud Functions emulator, you can override environment variables for your project by setting up a .env.local file. Contents of .env.local take precedence over .env and the project-specific .env file.

For example, a project could include these three files containing slightly different values for development and local testing:

`.env`	`.env.dev`	`.env.local`
PLANET=Earth AUDIENCE=Humans	AUDIENCE=Dev Humans	AUDIENCE=Local Humans

When started in the local context, the emulator loads the environment variables as shown:

  $ firebase emulators:start
  i  emulators: Starting emulators: functions
  # Starts emulator with following environment variables:
  #  PLANET=Earth
  #  AUDIENCE=Local Humans

Secrets and credentials in the Cloud Functions emulator

The Cloud Functions emulator supports the use of secrets to store and access sensitive configuration information. By default, the emulator will try to access your production secrets using application default credentials. In certain situations like CI environments, the emulator may fail to access secret values due to permission restrictions.

Similar to Cloud Functions emulator support for environment variables, you can override secrets values by setting up a .secret.local file. This makes it easy for you to test your functions locally, especially if you don't have access to the secret value.