Environment variables

This list is taken from the source of the fireemu binary and the npm package. Anything not listed here is an implementation detail and may change.

Set by fireemu exec

exec gives its command the variables of the emulators that are running, and nothing else of its own. Variables for emulators that are not selected are left as your environment had them, so a missing emulator never sends an SDK to production by accident. The names and formats follow what firebase emulators:exec writes.

Variable	Value	When
FIRESTORE_EMULATOR_HOST, FIREBASE_FIRESTORE_EMULATOR_ADDRESS	Firestore host:port	Firestore runs
FIREBASE_AUTH_EMULATOR_HOST	Authentication host:port	Authentication runs
FIREBASE_STORAGE_EMULATOR_HOST	Storage host:port	Storage runs
STORAGE_EMULATOR_HOST	Storage URL (http://host:port) for the Cloud Storage client libraries. With Storage App Check enforced and appCheck.storageServerRequests set to "capability" it also carries a per-run Admin capability (see App Check)	Storage runs
FIREBASE_DATABASE_EMULATOR_HOST	Realtime Database host:port	The Realtime Database runs
PUBSUB_EMULATOR_HOST	Pub/Sub host:port	Pub/Sub runs
CLOUD_EVENTARC_EMULATOR_HOST	Eventarc URL (http://host:port)	Functions run
CLOUD_TASKS_EMULATOR_HOST	Cloud Tasks host:port	Functions run
FIREEMU_FUNCTIONS_HOST	Functions host:port	Functions run
FIREEMU_APP_CHECK_EMULATOR_HOST, FIREEMU_APP_CHECK_JWKS_URL	App Check exchange host and JWKS URL	App Check is available (see App Check)
FIREBASE_EMULATOR_HUB	Emulator Hub host:port	The Hub runs
FIREBASE_LOGGING_EMULATOR_HOST	Logging emulator host:port	The Logging emulator runs
GCLOUD_PROJECT, GOOGLE_CLOUD_PROJECT	The project ID	Always
FIREBASE_CONFIG	Set from the project ID	Unless your environment already has it
FIREEMU_CONTROL_URL	Base URL of the control API, ending in /v1/	Always
FIREEMU_CONTROL_TOKEN	Bearer token for the control API; used by fireemu/testing and by the scripts in Cloud Firestore	Always

fireemu up does not set variables in your shell. Its startup output prints each host:port (for example FIRESTORE_EMULATOR_HOST=127.0.0.1:8080), and the Emulator UI shows them on the Overview page under “Environment for SDKs”.

Set for Functions code

A Functions codebase runs with the same emulator host variables for the services that are running, plus FUNCTIONS_EMULATOR=true, the project ID variables and FIREBASE_CONFIG. Only a short list of variables is inherited from the daemon. Credentials are withheld on purpose: GOOGLE_APPLICATION_CREDENTIALS, FIREBASE_TOKEN and CLOUDSDK_* do not reach function code. The FIREEMU_RUNNER* variables are internal.

Read by Fireemu

Variable	Effect
FIREEMU_BINARY_PATH	The fireemu launcher runs this binary instead of the platform package’s. For a platform without a published binary, or a binary you built.
FIREEMU_NODE	Absolute path of the Node.js executable that runs Functions codebases. Refused when it is not an absolute path to an executable file. Without it, Fireemu looks for node in the PATH directories (and Volta’s, see VOLTA_HOME).
FIREEMU_RUNNER_NODE, FIREEMU_RUNNER_PYTHON	Path of a Functions runner script (index.mjs, runner.py) to use instead of the bundled one. An error when the file does not exist.
FIREEMU_WORKER_THREADS	Number of async worker threads, 1 to 64. Default: the number of available cores, at most 4.
FIREEMU_MAX_BLOCKING_THREADS	Upper bound of blocking threads, 1 to 512. Default: 64.
FIREEMU_CONTROL_TOKEN	fireemu doctor --connect sends it as the bearer token to the control API. Inside fireemu exec it is already set.
FIREBASE_CONFIG	When exec finds it set, it keeps your value instead of writing one from the project ID.
PATH, VOLTA_HOME	Where Node.js is looked for when FIREEMU_NODE is not set.
HOME, XDG_CACHE_HOME, LOCALAPPDATA	Where the cache of the Authentication session signing key is kept (an owner-only directory); without a usable cache the key is generated in memory at each start.
SUDO_UID	When Fireemu runs as root, the user named here is also a trusted owner of discovered configuration files. See file ownership checks.
ComSpec	On Windows, the shell that runs the script form of fireemu exec "script". Default: cmd.exe.
FIREEMU_TRACE_WEBCHANNEL, FIREEMU_TRACE_STORAGE	Any value prints a request trace ([webchannel] ..., [storage] ...) on standard error, for diagnosing a client problem. Not for regular runs.