functions-framework-dart

This is the framework that makes it work. It gives you a local development server and the scaffolding to write HTTP and CloudEvent handlers that deploy directly to Cloud Functions or Cloud Run.

Apache 2.0, Google-maintained. It's a thin layer. You write a Dart function, annotate it, and the framework handles the HTTP server, request parsing, and function routing. Works with the Dart package ecosystem via pub.dev.

Fully free. No paid tier exists. It's a framework, not a service. You pay Google Cloud for compute when you deploy, but the framework itself costs nothing. Solo Dart developers experimenting with serverless: useful if you're committed to Dart on the backend. Small teams: only makes sense if your whole stack is Dart (Flutter front + Dart backend). Larger teams: almost certainly using Node, Python, or Go for Cloud Functions already.

The catch: the Dart serverless ecosystem is tiny, and zero velocity tells you adoption is niche. If your function needs packages that don't exist in Dart, you're stuck. Node.js or Python Cloud Functions have 100x the community support.