Fern is a code generation platform that transforms API definitions into production-ready SDKs and documentation.
Fern solves the problem of maintaining multiple SDKs and API documentation in sync with your API specification. It takes OpenAPI, AsyncAPI, Protobuf, or OpenRPC definitions as input and generates type-safe SDKs in TypeScript, Python, Java, Go, Ruby, PHP, and C#, along with interactive developer documentation. The approach is specification-driven: you define your API once, and Fern generates all downstream artifacts automatically, eliminating manual synchronization work.
Teams should adopt Fern if they maintain APIs and want to reduce the effort of SDK generation and documentation maintenance across multiple languages. It suits projects where consistency across SDKs matters and where you want to ship documentation alongside code. The tool includes built-in features like interactive API reference generation, markdown-based additional pages with git versioning, search functionality, dark mode, and customizable branding. The platform also offers AI-powered search trained on your documentation, APIs, and SDKs to answer developer questions automatically.
The project maintains active development with regular updates to its SDK generators and documentation features. The codebase shows consistent refinement of the code generation pipeline and expansion of supported API specification formats. Development activity indicates ongoing investment in both the core generation engine and the ecosystem of available generators that users can add to their workflows.
