ConnectRPC — Simple Browser-Compatible RPC over HTTP

Introduction

ConnectRPC simplifies RPC by building on standard HTTP. It generates type-safe clients and handlers from Protobuf schemas, and each server simultaneously speaks three protocols—Connect (simple HTTP), gRPC, and gRPC-Web—so browsers, mobile apps, and backend services all hit the same endpoint.

What ConnectRPC Does

• Generates type-safe client and server code from Protobuf service definitions
• Serves the Connect, gRPC, and gRPC-Web protocols on a single port and handler
• Works with net/http in Go, requiring no special HTTP server or mux
• Supports unary, server-streaming, client-streaming, and bidirectional streaming RPCs
• Provides interceptors for authentication, logging, and observability middleware

Architecture Overview

ConnectRPC generates handler and client code via protoc-gen-connect-go (Go), @connectrpc/connect (TypeScript), or plugins for other languages. Handlers register as standard HTTP handlers, detecting the protocol from each request's Content-Type header. The Connect protocol uses simple HTTP POST with JSON or Protobuf bodies—curl-friendly without special tooling. gRPC and gRPC-Web requests on the same endpoint are handled transparently.

Installation & Configuration

• Install the Buf CLI and protoc-gen-connect-go for Go code generation
• Use @connectrpc/connect and @connectrpc/connect-web for TypeScript clients
• Register handlers on any http.ServeMux or router—no proprietary server needed
• Configure TLS and HTTP/2 via standard Go net/http or your preferred reverse proxy
• Add interceptors in the handler or client constructor for cross-cutting concerns

Key Features

• Three protocols (Connect, gRPC, gRPC-Web) from a single handler implementation
• Browser-native: the Connect protocol works with fetch() without a proxy
• curl-friendly: curl -X POST --json works against Connect endpoints
• Standard HTTP middleware compatibility (no gRPC-specific interceptor chains)
• Streaming support across all three protocols including bidirectional

Comparison with Similar Tools

• gRPC-Go — requires grpc.NewServer() and HTTP/2; ConnectRPC uses net/http and adds browser support
• Twirp — Protobuf-based RPC by Twitch; unary only, no streaming or gRPC compatibility
• gRPC-Web — requires an Envoy or grpc-web proxy for browsers; ConnectRPC serves browsers directly
• tRPC — TypeScript-native RPC without Protobuf; ConnectRPC provides cross-language schemas
• REST/OpenAPI — manual endpoint design; ConnectRPC auto-generates clients and servers from a schema

FAQ

Q: Can I call ConnectRPC services from a browser? A: Yes. The Connect protocol uses standard HTTP and works natively with fetch(). The TypeScript client library handles serialization.

Q: Do I need Envoy or a special proxy? A: No. ConnectRPC handlers serve gRPC, gRPC-Web, and Connect directly on standard HTTP, eliminating the need for a translation proxy.

Q: Which languages does ConnectRPC support? A: Go, TypeScript/JavaScript, Swift, and Kotlin have official client and server libraries. The Connect protocol is simple enough for any HTTP client.

Q: Is ConnectRPC compatible with existing gRPC services? A: Yes. ConnectRPC clients can call standard gRPC servers, and ConnectRPC servers accept standard gRPC clients.

Sources

• https://github.com/connectrpc/connect-go
• https://connectrpc.com/