Fern is a platform for generating software development kits (SDKs), also called client libraries, and application programming interface (API) documentation. Developer-focused companies build with Fern, typically starting by uploading their OpenAPI or Swagger specifications. Fern supports generating SDKs in popular programming languages, including Python, TypeScript, Java, Go, C#, and Ruby. Fern is open source and backed by Y Combinator. Fern has native integrations with GitHub, Postman, NPM, PyPI, Nuget, and RubyGems.