Share
What is Fern?
Fern is a platform that generates SDKs, API docs and a CLI from a single spec such as OpenAPI, AsyncAPI or gRPC. The idea is that every surface developers and AI agents use to reach your API comes from one source of truth and stays in sync without manual work.
What is Fern used for?
It lets an API company stop hand-maintaining client libraries and reference pages. You point Fern at your spec, configure each language in a fern.yaml file, and fern generate produces the SDKs and publishes them to npm, PyPI, Maven Central, NuGet, RubyGems, Packagist, CocoaPods and crates.io. Every spec change regenerates everything.
What do Fern SDKs include?
- Strongly typed clients in TypeScript, Python, Go, Java, C#, Ruby, PHP, Swift and Rust.
- Pagination helpers and retries with backoff.
- OAuth with token refresh and bearer auth.
- File uploads, streaming and idempotency keys.
- Forward compatibility, so old clients survive additive changes.
What does AI do in Fern docs?
Docs sites ship with Ask Fern, a chat that answers from your content, and Fern Agent, a Slack-based agent that proposes edits as GitHub pull requests. Docs can also be translated with AI and expose llms.txt and an MCP server so Claude, Cursor and other clients can query your API.
Who is Fern for?
Platform and developer relations teams that ship public APIs. The site lists Square, Auth0, ElevenLabs, Adobe, Samsara and Twilio among its users. Large organizations can ask for SSO, SCIM, multiple repos and even self-hosting.
Fern pros and cons
- Pro: one source for SDKs, docs, CLI and MCP
- Pro: idiomatic SDKs in 9 languages
- Pro: automatic publishing to package registries
- Con: the entry SDK tier only covers Python and TypeScript
- Con: WebSockets, webhooks and custom SDK code are Enterprise-only
Fern features and use cases
How to use Fern
Fern FAQ
What is Fern?
Fern is a platform that generates SDKs, API documentation and a CLI from a single API specification.
Is Fern free?
Yes, both Docs and SDKs have a free-forever tier, while advanced features sit in Enterprise with custom pricing.
Which languages can Fern generate SDKs in?
TypeScript/JavaScript, Python, Go, Java, C#, Ruby, PHP, Swift and Rust, with Python and TypeScript on the free tier.
Which API specs does Fern support?
OpenAPI, AsyncAPI, gRPC, GraphQL and OpenRPC, plus OpenAPI overlays for customizing references.
What is Ask Fern?
It is the AI chat built into Fern docs sites that answers user questions from your own content.
What does Fern Agent do?
It is a Slack-based writing agent that proposes documentation changes as GitHub pull requests for your team to review.
Is Fern built for AI agents?
Yes, it publishes llms.txt, Markdown versions of every page and an MCP server for Claude, Cursor and other clients.
Can Fern be self-hosted?
Yes, the Docs Enterprise tier offers dedicated infrastructure with a self-hosting option for regulated teams.
What are the best Fern alternatives?
On GptZone you can compare it with Mintlify and GitBook for the documentation side.
Fern pricing and plans
Prices in US dollars (USD). Checked on: 02/11/2026. Docs and SDKs are priced separately.
Docs Free: $0 forever; 10 team members, 1,000 pages, 250 AI credits per month, 2,000 page generations per month, custom domain, Ask Fern, Fern Agent and MCP server.
Docs Enterprise: custom pricing; SSO, SCIM, multiple repos, custom components, advanced analytics and self-hosting.
SDK Free: $0 forever; Python and TypeScript SDKs, up to 200 REST endpoints and automated publishing.
SDK Enterprise: custom pricing per SDK billed annually; unlimited endpoints, 10 languages, WebSockets and webhooks.
Paying Postman customers can apply for Postman Team, with higher allowances than Free.
Fern Screenshots
Fern user reviews
Write a review
Checking your session...
Fern Reviews
Loading reviews...
Fern alternatives
OpenRouter
OpenRouter is a unified API that connects to 600+ text, image, video and audio models from 80+ providers with a single key and a single balance.