Fern

Fern is a developer toolkit that automatically generates beautiful API documentation and client SDKs from your API definition, helping companies make their APIs delightful to adopt and integrate. For any business that offers an API, two things drive developer adoption: clear, attractive documentation, and ready-made client libraries (SDKs) in the languages developers use. Producing and maintaining both by hand is tedious and error-prone, and they tend to drift out of sync with the actual API. Fern automates this, keeping everything consistent and up to date from a single source of truth.

The way it works is powerful. You define your API (using OpenAPI or Fern's own definition format), and Fern generates idiomatic, type-safe SDKs in multiple languages — like TypeScript, Python, Java, Go and more — so the developers consuming your API can integrate quickly without writing boilerplate HTTP code. At the same time, Fern produces polished, interactive API documentation that stays aligned with your API, complete with examples and a clean reading experience. Because both the SDKs and docs are generated from the same definition, they remain accurate and synchronized as your API evolves.

This makes Fern especially valuable for API-first companies, developer-tools startups, and any organization whose product is or includes an API, where developer experience directly affects adoption and success. By removing the manual burden of writing and maintaining SDKs and docs, Fern lets teams ship a professional, easy-to-integrate API with far less effort, and frees engineers to focus on the API itself rather than its scaffolding. As APIs become central to how software connects and companies grow through developer ecosystems, tools that elevate API developer experience are increasingly important. For teams that want their API to be easy and pleasant to adopt — with great docs and SDKs generated automatically and kept in sync — Fern offers an excellent, modern solution.