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Fern: SDKs and Docs for your API

buildwithfern.com5 min readsaved Feb 19, 2026
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TL;DR

Fern generates idiomatic SDKs (TypeScript, Python, Go, Java, Ruby, C#, PHP) and branded API docs from your OpenAPI spec. SDKs are language-native with OAuth, pagination, SSE, retries, and CI/CD publishing built in. Used by Cohere, Vapi, ElevenLabs. Recently joined Postman.

Why it matters

If you have a public API and want serious developer adoption, this is the fastest path to polished multi-language SDKs and docs without building and maintaining them manually.

Key points

  1. 1

    Generates SDKs in 8 languages from OpenAPI/gRPC/AsyncAPI — not generic wrappers but language-idiomatic code

  2. 2

    Auto-publishes to npm, PyPI, Maven, etc. with semantic versioning via CI/CD

  3. 3

    Docs platform: API reference, AI search, API key injection, RBAC, preview deployments, WebSocket support

  4. 4

    Add custom code to generated SDKs — your additions survive regeneration

  5. 5

    Clients claim $600K saved in engineer salaries; recently joined Postman for wider reach

SDKAPIdeveloper toolsOpenAPIdocumentationTypeScriptPythonFern