Fern
Input OpenAPI. Output production-ready SDKs and beautiful API docs — automatically, in nine languages.
Overview
Fern is an open-source SDK generation and API documentation platform that takes OpenAPI (and other API specs) as input and produces idiomatic, type-safe client libraries in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust — alongside polished, interactive developer documentation. Founded in 2022 by Danny Sheridan and Deep Singhvi (University of Michigan alumni, YC W23), Fern raised $13 million total before being acquired by Postman in January 2026, giving it access to Postman's 500,000+ organisations worldwide.
Post-acquisition, the Fern product, brand, and 25-person team operate intact under Postman. The platform supports REST (OpenAPI), WebSockets (AsyncAPI), gRPC, Server-Sent Events, and OpenRPC; automatically publishes SDKs to npm, PyPI, Maven, and other registries; and includes AI-native features such as embedded AI search, auto-generated MCP servers, and llms.txt generation — positioning it directly in the agentic API tooling wave.
Pricing
Pricing shown for reference only. These figures reflect RECATOOLS research as of 31 Aug 2026 and may be out of date or incomplete. This is not financial or purchasing advice — always confirm the current price on the provider’s official website before making any decision.
- 2 team members
- 250 AI credits
- Custom domain
- API explorer + web editor
- 5 team members
- 1,000 AI credits
- Version/product switching
- Password protection
- SSO + RBAC
- Self-hosting
- Dedicated support channel
- Translated content
Use cases
What you can produce with Fern
- Production-ready, idiomatic SDKs auto-published to npm / PyPI / Maven / other registries on each API change
- Interactive API documentation site with built-in explorer, versioning, changelog, and custom domain
- AI-powered in-docs search (Ask Fern) with 250–1,000 credits included in free/team plans
- Auto-generated MCP server stubs and llms.txt for agent-first API discoverability
- Multi-protocol support coverage across REST, WebSockets, gRPC, SSE, and OpenRPC from a single spec
- SDK user-facing features including auth handling, automatic retries with exponential backoff, pagination helpers, and streaming support
- Enterprise-grade access controls: visitor authentication (JWT/SSO), RBAC, password-protected docs, and self-hosting option
ASEAN Perspective
Fern in Southeast Asia
Fern has no dedicated ASEAN presence, local pricing, or regional support tier as of mid-2026, and its known customer logos (Square, Auth0, Adobe, Twilio, ElevenLabs, Cohere, Pinecone) are predominantly US-headquartered. That said, APAC API-first companies — particularly in Singapore's fintech and developer-tool sectors — are likely adopters via Postman's distribution, given Postman's long-standing APAC usage. Teams in the region can start free (Hobby plan) and evaluate SDK output quality before committing to the $150/month Team plan; documentation is in English only.
Nordic APIs picked Fern as the best of eight SDK generators it tested in 2025, and the reasoning holds up: the output reads like a senior engineer wrote it by hand, not a template. The open-source core (Apache 2.0, 3.7k GitHub stars) and a genuinely free Hobby tier make it easy to try before committing. Postman bought Fern in January 2026 for an undisclosed sum, saying the 25-person team and product stay independent — a promise that's easy to make and harder to keep three years out. The bigger practical snag is pricing: Hobby is free, then Team jumps straight to $150/month with nothing in between. There's no drag-and-drop console either — everything runs through the CLI, which suits API teams fine and frustrates anyone hoping for a GUI.
What people say
Eight SDK generators went through Nordic APIs' 2025 shootout, and Fern came out on top alongside APIMatic — reviewers called the generated code "clean, well-organized, and ... hand-written with precision and care." That's the core case for Fern: teams stop hand-maintaining SDKs in nine languages and get libraries that pass code review without embarrassment.
The open-source core is Apache 2.0 licensed with 3.7k stars on GitHub and steady commit activity into 2026, and the Hobby plan is free forever for two seats — a real trial, not a seven-day countdown. Postman acquired Fern in January 2026 for an undisclosed sum, an investment that predates the deal since Postman CEO Abhinav Asthana was an early backer. Postman says Fern keeps its own brand, product, and 25-person team, and the deal does extend distribution to Postman's 500,000-plus customer base, including 98% of the Fortune 500.
Money is the sharper edge. Hobby costs nothing, but Team starts at $150 a month with no step in between, and SDK generation is priced separately from docs — one comparison piece pegs SDK plans starting around $250/month per SDK. There's no visual builder: generation runs through a CLI and YAML config, which developer teams tend to like and less technical teams don't. Support for ASEAN-specific billing currencies, localized documentation SLAs, or a regional presence isn't advertised, so APAC teams adopt Fern on the strength of the generated code rather than any regional tailoring.
Summary of public user & expert reviews, compiled by RECATOOLS.
Notable facts
- Fern's founders Danny Sheridan and Deep Singhvi built a $3M/year Amazon e-commerce business together before pivoting to developer tooling.
- The GitHub repo had logged 2,463 releases by May 2026 — averaging roughly one release per day since launch.
- Fern generates SDKs in nine languages from a single spec; the repo itself is 76% TypeScript with Rust handling performance-critical generation paths.
- Postman acquired Fern on 8 January 2026 — just nine months after Fern closed its $9M Series A led by Bessemer Venture Partners.
Frequently asked questions
About this listing
This entry was compiled from publicly available data including Fern's official website, press releases, documentation, and reputable third-party publications. RECATOOLS is not affiliated with Fern unless explicitly stated.
Third-party AI tools update their pricing, features, availability, and policies frequently. Information here may be outdated by the time you read this — we make reasonable efforts to keep listings current, but cannot guarantee absolute accuracy.
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