Fern
Input OpenAPI. Output SDKs in up to ten languages, API docs and CLIs — now a Postman company.
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, with Kotlin in progress — alongside interactive developer documentation and, now, command-line tools. Founded in 2022 by Danny Sheridan, Deep Singhvi and Zach Kirsch (YC W23), Fern raised more than $12 million before Postman acquired it in January 2026; it continues as an independent product.
The platform supports REST (OpenAPI), WebSockets (AsyncAPI), gRPC, Server-Sent Events, OpenRPC and GraphQL; publishes SDKs to npm, PyPI, Maven and other registries; and includes AI features such as Ask Fern search, a hosted MCP server that answers questions from your docs, and llms.txt generation. Free tiers cover docs and Python and TypeScript SDKs; everything else is custom-priced Enterprise.
Pricing
Pricing shown for reference only. These figures reflect RECATOOLS research as of 28 Sep 2026 and may be out of date or incomplete.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.
- 10 team members, 1,000 pages
- 250 AI credits a month
- Custom domain, API explorer and web editor
- Up to 200 endpoints
- REST only
- Automated registry publishing
- SSO, SCIM and RBAC
- Self-hosting
- All ten SDK languages, unlimited endpoints
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 AI credits a month on the free plan
- A hosted MCP server that answers questions from your docs, plus llms.txt, for agent-first API discoverability
- Multi-protocol support across REST, WebSockets, gRPC, SSE, OpenRPC and GraphQL
- SDK user-facing features including auth handling, automatic retries with exponential backoff, pagination helpers, and streaming support
- Enterprise access controls — visitor authentication (JWT/SSO), RBAC and self-hosting — with password protection available on the free plan
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.
A 2025 Nordic APIs review of eight SDK generators, by guest author Alvaro Tejada Galindo, picked Fern as its top SDK generator, 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) and genuinely free docs and SDK tiers make it easy to try before committing. Postman bought Fern in January 2026 for an undisclosed sum, saying it will continue as an independent product — a promise that's easy to make and harder to keep three years out, and the pricing has already been reshaped: the $150-a-month Team plan and the per-SDK Basic and Pro plans are gone, leaving free tiers and custom-priced Enterprise with nothing in between. SDK generation runs through a CLI, which suits API teams fine; docs at least get a web editor.
What we found
Eight SDK generators went through a 2025 review for Nordic APIs by Alvaro Tejada Galindo, and Fern was his top pick for SDK generation — he 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 as many as ten languages and get libraries that pass code review without embarrassment.
The open-source core is Apache 2.0 licensed, with commits landing on GitHub as recently as late September 2026, and the free docs plan now covers ten team members and 1,000 pages — a real tier, 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 will continue to operate as an independent product; its team, 25 at the deal, is now under 40 people in Brooklyn, and the deal extends distribution to the more than 500,000 companies that use Postman, including 98% of the Fortune 500.
Money is the sharper edge. Between July and September 2026 Fern removed its $150-a-month Team plan and its $250 and $600 per-SDK plans, leaving free tiers and custom-priced Enterprise for both docs and SDKs; the free SDK tier covers only Python and TypeScript, up to 200 endpoints. SDK generation runs through a CLI and YAML config, though docs can be edited in a web editor, which helps less technical teams. 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.
More than 200 customers use it, Square, Auth0, Adobe, Twilio and ElevenLabs among them, and Fern now also generates a command-line tool from an API definition. Existing Postman customers can apply for a zero-cost Postman Team plan with higher limits.
Compiled by RECATOOLS from public sources: vendor documentation and pricing, code repositories and published reporting.
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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