Fern, a language for defining REST APIs that compiles into OpenAPI
Hi HN, this is Danny, Deep, and Zach. We built Fern after our previous ed tech startup failed. We were frustrated with how much time we spent writing “API code” instead of working on the actual product. We tried to use OpenAPI but we were underwhelmed - the generated code wasn’t idiomatic and it still required manual work (custom templates, scripts, manually publishing SDKs to registries). The Fern compiler takes your API as input and invokes generators that output things like: SDKs, server code, a Postman collection, and an OpenAPI spec. Some technical highlights about the compiler +…
Fern, a language for defining REST APIs that compiles into OpenAPI launched on January 11, 2023 with 18 votes, #1,294 of 3,901 launches that month and more than 75% of that year's launches. The site was still online in September 2026, 3 years on.
In plain words
Fern is a language and compiler for defining REST APIs that automatically generates SDKs, server code, Postman collections, and OpenAPI specifications. Designed for developers who want to spend less time on API boilerplate, it validates API definitions for correctness and best practices before generating idiomatic code across multiple languages and formats. The tool aims to reduce manual work typically required with standard OpenAPI approaches.
written from the facts on this page · September 2026
From the sources
Input OpenAPI. Output SDKs and Docs. Contribute to fern-api/fern development by creating an account on GitHub.
In the maker’s words, at launch
Hi HN, this is Danny, Deep, and Zach. We built Fern after our previous ed tech startup failed. We were frustrated with how much time we spent writing “API code” instead of working on the actual product. We tried to use OpenAPI but we were underwhelmed - the generated code wasn’t idiomatic and it still required manual…
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