[!WARNING]
This open-source project is no longer maintained.
For access to Fern's SDK, CLI, MCP, and Docs generation, sign up at buildwithfern.com.
🌿 What is Fern?
Fern is a platform that transforms your API definitions into production-ready SDKs and beautiful documentation in minutes.
With Fern, you can offer your users:
- 🧩 Type-safe SDKs in multiple languages, including TypeScript, Python, Java, Go, Ruby, PHP, and C#
- 📘 Developer documentation featuring an interactive UI and auto-generated API + SDK references
- ✨ AI Search powered by an assistant trained on your docs, APIs, and SDKs that can instantly answer a developer's questions
Fern supports leading API specifications including OpenAPI (REST, Webhooks), AsyncAPI (WebSockets), Protobuf (gRPC), and OpenRPC.
🌿 SDKs
The Fern platform is available via a command line interface (CLI) and requires Node 18+. To install it, run:
npm install -g fern-api
Initialize Fern with your OpenAPI spec:
fern init --openapi ./path/to/openapi.yml
# or
fern init --openapi https://link.buildwithfern.com/plantstore-openapi
Your directory should look like the following:
fern/
├─ fern.config.json
├─ generators.yml # generators you're using
└─ openapi/
└─ openapi.json # your openapi document
Finally, to invoke the generator, run:
fern generate
🎉 Once the command completes, you'll see your SDK in /generated/sdks/typescript.
🌿 API Documentation
Fern can also build and host a documentation website with an auto-generated API reference. Write additional pages in markdown and have them versioned with git.
Search, SEO, dark mode, and popular components are provided out-of-the-box. Plus, you can customize the colors, font, logo, and domain name.
Check out docs built with Fern:
Get started here.
🌿 Generators
Generators are processes that take your API Definition as input and output artifacts (SDKs, Server boilerplate, etc.). To add a generator, run fern add <generator id>.
SDK Generators
CLI Generators
Fern's CLI generator produces a standalone command-line interface for your API.
This is the beginning of the README. Read the rest at the original. Read the full README ↗
