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Introduction

Connect is a family of libraries for building browser and gRPC-compatible HTTP APIs: you write a short Protocol Buffer schema and implement your application logic, and Connect generates code to handle marshaling, routing, compression, and content type negotiation. It also generates an idiomatic, type-safe client in any supported language.

Production-grade simplicity​

Each Connect implementation is focused: just the essential features, built on top of time-tested HTTP libraries and designed to get out of your way. In Go, Connect is just one package — short enough to read in an afternoon.

Connect is our vision of production-grade RPC. It's simple, reliable, and unobtrusive, because nobody has time to debug overcomplicated networking or sift through a hundred esoteric options. Under the hood, it's just Protocol Buffers and net/http, fetch, URLSession, or your language's gold standard for HTTP.

Most of all, Connect is stable. We take backward compatibility very seriously, and we'll never break your build after tagging a stable release.

Seamless multi-protocol support​

Connect servers and clients support three protocols: gRPC, gRPC-Web, and Connect's own protocol.

  • Connect fully supports the gRPC protocol, including streaming, trailers, and error details. Any gRPC client, in any language, can call a Connect server, and Connect clients can call any gRPC server. We validate our gRPC compatibility with an extended version of Google's own interoperability tests.

  • Connect also offers direct support for the gRPC-Web protocol used by gRPC/gRPC-Web, without relying on a translating proxy like Envoy.

  • Finally, Connect supports its own protocol: a straightforward HTTP-based protocol that works over HTTP/1.1 and HTTP/2. It takes the best parts of gRPC and gRPC-Web, including streaming, and packages them into a protocol that's equally at home in browsers, monoliths, and microservices. The Connect protocol is what we think the gRPC protocol should be. By default, JSON- and binary-encoded Protobuf is supported. You can call our live demo service with cURL:

    curl \
        --header "Content-Type: application/json" \
        --data '{"sentence": "I feel happy."}' \
        https://demo.connectrpc.com/connectrpc.eliza.v1.ElizaService/Say

By default, Connect servers support ingress from all three protocols. Clients default to using the Connect protocol, but can switch to gRPC or gRPC-Web with a configuration toggle — no further code changes required. The APIs for errors, headers, trailers, and streaming are all protocol-agnostic.

Go​

Connect's Go implementation is stable and used by several companies (including Buf) in production. You can get started with connect-go now.

TypeScript and JavaScript​

Connect for ECMAScript is currently pre-v1, but we have been using it on the web in production for a while. We plan to release a stable v1 in early 2023. However, you can get started now.

Connect for Node is currently in beta. We plan to release a stable v1 alongside Connect for Web. You can get started with connect-node now.

Swift and Kotlin​

We believe Protobuf should be the best choice for API development at every layer of the stack, and this includes mobile clients.

To this end, both connect-swift and connect-kotlin are now available in beta, and you can get started today with the Swift getting started guide and the Kotlin getting started guide!

What's next?​

In addition to improving our current suite of Connect products and moving our beta products to a stable v1, eventually, we'd like to release Connect implementations for Rails, Django, Laravel, and similar frameworks.

You shouldn't have to choose between these productive toolkits and Protocol Buffers — they should work seamlessly together.