# fern-api/fern

Input OpenAPI. Output SDKs and Docs.

Repository: https://github.com/fern-api/fern
Canonical: https://ross.abutalabs.com/products/fern
Homepage: https://buildwithfern.com
Language: TypeScript
License: Apache-2.0
License Family: permissive
Topics: sdk-generator, openapi, docs-generator, api, docs-as-code
Last push: 2026-08-26T22:55:17+00:00

## Health v2 (maintenance only)
Score: 89/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 71, longevity 100
- inputs: {"age_days": 1615, "days_push": 7, "days_rel": 113, "gap_med": 0.0, "n_releases_24m": 1277}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3764, forks 339 (observed 2026-08-28T04:08:17.978240+00:00)

## What it is
Fern is a CLI-based platform that takes OpenAPI (and AsyncAPI, Protobuf, OpenRPC) definitions and generates type-safe SDKs in multiple languages plus developer documentation with API references. It is distributed as an npm package and runs on Node 18+.

## Use cases
- generate sdks from openapi spec
- generate api documentation from openapi
- create typescript and python client libraries for my api
- keep sdk and docs in sync with api definition
- generate multi-language sdks for rest api
- build developer docs with api reference
- docs as code pipeline for api

## When to choose
- you maintain a public or internal API and want to ship SDKs in several languages
- you want documentation and SDKs generated from a single API definition
- you use OpenAPI, AsyncAPI, Protobuf, or OpenRPC specs
- you want docs-as-code with CI-friendly generation

## When to avoid
- you don't have a machine-readable API definition
- you need fully hand-crafted SDKs with custom idioms beyond what generators produce
- you only need a static site generator unrelated to APIs

## Facets
- artifact type: cli-tool
- maturity: active
- function: sdk, documentation, api-documentation, cli
- domain: developer-tools, apis, web-development, documentation
- platform: cli, cross-platform
- tags: sdk-generator, openapi, docs-as-code, api-reference, multi-language-sdks, code-generation, nodejs

## Member repositories
- fern-api/fern (main) score 89

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:17.978240+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:28:37.126829+00:00, confidence not recorded.
  - readme: https://github.com/fern-api/fern (fetched 2026-08-28T04:08:17.978240+00:00, sha f8403a52e357)
  - homepage: https://buildwithfern.com (fetched 2026-08-29T09:23:05.630099+00:00, sha 44136fa355b3)
- Data as of 2026-08-30T08:39:29.467469+00:00.