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 These figures reflect RECATOOLS research as of 16 Jun 2026 and may be out of date or incomplete.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.
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.
Fern earns its strong scores on raw capability and code quality: independent reviewers consistently describe the generated SDKs as clean, idiomatic, and indistinguishable from hand-written libraries — an outcome that saves API teams weeks of maintenance toil. The open-source core (Apache 2.0, 3.7k GitHub stars, actively maintained as of May 2026) and a permanently free Hobby plan make it accessible to startups, while the January 2026 Postman acquisition extends its distribution to 500,000+ organisations. SOC 2 Type II compliance adds enterprise confidence.
Caveats exist. The platform is CLI-first with no rich web UI for SDK generation, which may steepen the learning curve for less terminal-fluent teams. Pricing jumps sharply at the Team tier ($150/month) with no mid-tier between free and $150. ASEAN-specific localisation, billing in local currencies, and regional support SLAs are not advertised, making it a globally-oriented product that APAC teams adopt on merit rather than regional tailoring. Postman integration promises broader reach but also introduces acquisition-risk uncertainty for long-term roadmap stability.
What people say
Fern is a strong choice for API teams that want clean, maintainable SDKs without manual upkeep. A 2025 Nordic APIs review of eight SDK generators named Fern its top pick, praising the generated code as "clean, well-organized, and ... hand-written with precision and care." The open-source Apache 2.0 core, free Hobby tier, and January 2026 acquisition by Postman bolster its viability. The main friction points are a steep jump from free to paid (Docs Team starts at $150/month, with SDK generation priced separately), a CLI-driven generation workflow with no GUI, and no APAC-specific support or localisation.
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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