Firenook

Firenook is an open-source, drop-in replacement for the Firebase Local Emulator Suite. It reads an existing firebase.json, .firebaserc, Security Rules and indexes, and serves Firestore, Authentication, Cloud Storage, Cloud Functions, Extensions, Pub/Sub, Cloud Tasks and Eventarc on the same ports as the official emulators, so client and Admin SDKs connect without code changes. It imports and exports the official emulator data format in both directions.

The emulated services are written in Rust and store data on disk instead of in a Java heap, so neither Java nor firebase-tools is required: it ships as a single npm package with native engines for Windows, macOS and Linux, while Node.js runs Cloud Functions. With the --keep-data option, Firestore, Auth and Storage data persists between restarts, and the developer reports much faster writes and lower memory use than the official emulator.

Firenook also includes a local web console for each service, a terminal view that traces every function call with its trigger, duration and errors, an emulators:exec command for CI test runs, and a built-in MCP server that lets coding agents such as Claude Code, Cursor or VS Code read and write data, manage users, inspect logs and debug Security Rules. Realtime Database, Hosting, App Hosting and Data Connect are not emulated.