Fern

Fern is a development platform that helps teams start from an OpenAPI specification and reliably generate production-ready SDKs and interactive API documentation. Its primary purpose is to streamline the process of exposing APIs to developers by keeping client libraries, documentation, and API contracts in sync as your backend evolves. Fern is designed to fit into modern engineering workflows, reducing the manual effort and maintenance overhead typically associated with multi-language SDKs and docs.

With Fern, you can generate strongly typed SDKs in multiple programming languages from a single OpenAPI definition, ensuring consistency across client implementations. The tool supports idiomatic code generation tailored to each language, including authentication handling, pagination helpers, error types, and request/response models. It also produces interactive API documentation that is directly driven by your OpenAPI spec, enabling developers to explore endpoints, view example requests and responses, and test calls in-browser. Fern integrates into CI/CD pipelines, so SDKs and docs can be automatically regenerated and published whenever your API specification changes.