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Firebase Functions

To deploy to Firebase, use the built-in firebase adapter. This adapter uses Firebase Cloud Functions (v2) with Firebase Hosting rewrites, bundling your server into a single edge file with full response streaming support.

You need the Firebase CLI installed:

npm install -g firebase-tools

# Login to Firebase
firebase login

No additional packages are needed — the adapter is built into @lazarv/react-server.

Your Firebase project must be on the Blaze (pay-as-you-go) plan to deploy Cloud Functions. You can upgrade in the Firebase Console.

Add the adapter to your react-server.config.mjs file:

export default {
  adapter: "firebase",
};

You can customize the adapter by passing options:

export default {
  adapter: [
    "firebase",
    {
      project: "my-project",       // Firebase project ID
      region: "us-central1",       // Function region
      memory: "512MiB",            // Memory allocation
      timeoutSeconds: 60,          // Request timeout
      minInstances: 0,             // Minimum warm instances
      maxInstances: 100,           // Maximum concurrent instances
      concurrency: 80,             // Requests per instance
      hosting: {},                 // Extra firebase.json hosting properties
      functions: {},               // Extra firebase.json functions properties
      firebase: {},                // Extra top-level firebase.json properties
    },
  ],
};

Configuration Options

You can also pass adapter options at deploy time via the --deploy flag:

pnpm react-server build --adapter firebase --deploy='{"project":"my-project"}'

Build and deploy in one step:

pnpm react-server build --deploy

Or build first and deploy manually:

# Build
pnpm react-server build

# Deploy using Firebase CLI
firebase deploy --only functions,hosting --project <project-id>

This adapter supports response streaming. React Server Components, Suspense boundaries, and progressive HTML delivery all work out of the box. The generated Cloud Function streams the response body chunk by chunk using the Node.js response object's write() method.

The adapter uses an edge build mode, bundling your entire server into a single file. At build time, it:

  1. Bundles your server into .firebase-app/server/.react-server/server/edge.mjs
  2. Copies all static assets into .firebase-app/public/
  3. Generates a src/index.mjs wrapper that:
    • Imports onRequest from firebase-functions/v2/https
    • Registers an HTTP-triggered function matching all methods and paths
    • Serves static files from a build-time route map using readFileSync()
    • Converts incoming Express-style requests to standard Request objects
    • Delegates dynamic requests to the bundled edge handler
    • Streams the response back
  4. Generates package.json with firebase-functions and firebase-admin dependencies
  5. Runs npm install in .firebase-app/ to install dependencies
  6. Generates firebase.json with Hosting rewrites pointing to the function
  7. Generates .firebaserc with the project ID (if available)

Important: The firebase-functions and firebase-admin packages cannot be bundled into the edge build. The Firebase Functions runtime expects these as external dependencies in node_modules.

Static files are served by Firebase Hosting's CDN when possible. All static assets (HTML, CSS, JS, images) are copied to .firebase-app/public/ and served directly by Hosting. The function also has a static file route map as a fallback for any requests that reach the function.

Assets under /assets/ and /client/ paths are served with immutable cache headers (Cache-Control: public, max-age=31536000, immutable).

After building, you can test locally using the Firebase Emulator:

firebase emulators:start --only functions,hosting

.firebase-app/
├── package.json              # Dependencies (firebase-functions, firebase-admin)
├── node_modules/             # Installed dependencies
├── public/                   # Static assets (HTML, CSS, JS, images)
├── server/
│   └── .react-server/        # Bundled server (edge.mjs, manifests)
└── src/
    └── index.mjs             # Firebase Cloud Function entry

firebase.json                 # Firebase configuration (Hosting + Functions)
.firebaserc                   # Firebase project alias

"Blaze plan required" error

Firebase Cloud Functions require the Blaze (pay-as-you-go) billing plan. Upgrade your project at the Firebase Console. The Blaze plan still includes generous free-tier usage — you only pay for actual usage beyond the free limits. The billing plan is per-project and does not affect your other Firebase projects.

Cold starts

By default, minInstances is 0, meaning the function scales to zero when idle. The first request after scaling to zero will experience a cold start (typically 1-3 seconds). Set minInstances: 1 to keep one instance warm:

export default {
  adapter: ["firebase", { minInstances: 1 }],
};

"Could not find project" error

Make sure your project ID is correct. You can list your Firebase projects with:

firebase projects:list

Set the project explicitly via adapter options or the --deploy flag:

pnpm react-server build --adapter firebase --deploy='{"project":"my-project"}'
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