Fern is a aPI & developer docs tool for Developers, offered as freemium. Founded in United States in 2022. Popular alternatives include Speakeasy.
About Fern
Fern is a Y Combinator-backed developer tools company that turns API definitions into SDKs and documentation. Postman acquired Fern in January 2026 and said the Fern product and brand would continue. Teams describe their API with an OpenAPI specification or Fern's own definition format, and Fern generates idiomatic client libraries in languages such as TypeScript, Python, Java, Go, C# and Ruby, plus a hosted documentation site whose API reference stays in sync with the spec.
Generation runs from the command line or in CI, so every API change can produce new SDK versions and publish them to registries such as npm, PyPI and Maven automatically. The docs product supports Markdown guides, interactive API playgrounds, versioning, custom domains and AI search over the content, so the same definition powers both code and documentation. A free plan covers documentation for small teams, while paid pricing is custom and depends on the number of SDK languages, endpoints and documentation needs, which places paid use closer to an infrastructure purchase than a self-serve tool.
Fern suits API-first companies that would otherwise dedicate engineers to maintaining hand-written SDKs in several languages. The output is only as good as the spec, so teams need a clean, well-maintained OpenAPI file, and relying on generated code creates some vendor dependence. Speakeasy and Stainless are the closest SDK-generation alternatives, while Mintlify, ReadMe and Redocly compete on the documentation side.
Key features of Fern
- SDK generation (TS, Python, Java, Go)
- Docs generation
- API definition
- CI publishing
- Versioning
- Examples
Pros and cons
Pros
- Saves SDK engineering
- Idiomatic code
- Docs included
- CI-friendly
Cons
- Enterprise pricing is custom
- Spec quality required
- Vendor dependence
- Learning curve
Fern pricing
Fern uses a freemium model.
| Plan | Price | Includes |
|---|---|---|
| Free | $0 | 10 team members, 1,000 pages, custom domain |
| Enterprise | Custom | SSO, SCIM, RBAC, self-hosting, SLA |
Source: buildwithfern.com · checked on Oct 20, 2026
How Fern compares in API & developer docs
- Rank by votes
- #2 / 16
- Starting price
- $0
- Free alternatives
- 4
0 votes from members
Category median is $38/mo
Free or open-source tools in API & developer docs
Fern ranks #2 of 16 api & developer docs tools by community votes and is not directly comparable on price.
Common use cases
- 1API company shipping SDKs
- 2Keeping docs in sync
- 3Multi-language clients
- 4Developer experience
Best for
API-first companies.
Not ideal for
Small internal APIs.
Integrations
- OpenAPI
- GitHub
- npm
- PyPI
- Maven
Our take
Fern automates SDKs and docs from your spec.
FAQ
- What is Fern?
- Fern is a API & developer docs tool: SDKs and docs generated from your API spec.
- How much does Fern cost?
- Fern uses a Freemium model; see the vendor's pricing page for current plans.
- What are the best alternatives to Fern?
- Community-listed alternatives to Fern include Speakeasy.
- What does Fern integrate with?
- Fern integrates with OpenAPI, GitHub, npm, PyPI, Maven and more.
- Which platforms does Fern support?
- Fern is available on web.
- Who is Fern for?
- API-first companies.
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