Fern
Fern generates API documentation sites, SDKs in nine languages, and agent-first CLIs from a single OpenAPI/AsyncAPI/gRPC spec. Acquired by Postman in January 2026, it serves 200+ enterprise and mid-market customers including Square, Adobe, Auth0, NVIDIA, and ElevenLabs.
- Company typePrivate
- Founded2022
- HeadquartersNew York, United States
- Headcount51–100
- GTM typeB2B
- OfferingSoftware
What Fern does
Fern is a developer-tools platform that generates API documentation websites, idiomatic client SDKs in nine programming languages, and branded agent-first command-line interfaces from a single source of truth (OpenAPI, AsyncAPI, OpenRPC, gRPC, or Fern Definition). The `fern generate` command compiles a spec into synchronized outputs — including a docs site, SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust, plus a CLI distributed via Homebrew, npm, pnpm, Scoop, and a curl installer. The platform is sold as a tiered subscription: a free Hobby tier, a $150/month Team tier with a 14-day free trial, and an Enterprise tier with custom pricing, SOC 2 Type II compliance, SAML/OIDC SSO, RBAC, self-hosting, and dedicated deployed engineers.
Fern serves more than 200 customers spanning enterprise and mid-market segments, including Square, Auth0, Adobe Frame.io, NVIDIA, Webflow, Deel, ElevenLabs, Merge, Deepgram, Unleash, Cohere, and Cash App. The company was founded in 2022, is Y Combinator-backed, raised a $9M Series A led by Bessemer Venture Partners in April 2025 (total capital $13M), and was acquired by Postman in January 2026. Fern operates as a Postman company under the legal entity Birch Solutions, Inc., headquartered in Brooklyn, NY, with a team of approximately 25 people. Go-to-market is product-led self-serve at the bottom and direct enterprise sales at the top, supported by free-tier funnels, SEO comparison content, open-source community presence on GitHub, and customer-migration services that embed Fern engineers with prospect teams.
Fern firmographics
Firmographics- Name
- Fern
- Legal name
- Birch Solutions, Inc.
- Website
- https://buildwithfern.com
- Company type
- Private
- Founded year
- 2022
- Operating status
- Acquired
- Headcount range
- 51–100 employees
- Short description
- Fern generates API documentation sites, SDKs in nine languages, and agent-first CLIs from a single OpenAPI/AsyncAPI/gRPC spec. Acquired by Postman in January 2026, it serves 200+ enterprise and mid-market customers including Square, Adobe, Auth0, NVIDIA, and ElevenLabs.
- Ownership category
- akta.pro rank
Where Fern is headquartered
LocationHeadquarters
- HQ city
- New York
- HQ country
- United States
- HQ region
- North America
Offices3 records
Markets served
Fern business model
Business model- GTM type
- B2B
- Offering type
- Software
- Cost components
- Personnel, Technology or R&D, Marketing or Sales, Operations, Infrastructure, Others
Revenue model
- Subscription SaaS (Docs product): Recurring monthly/annual subscription across three tiers: Hobby ($0/mo, free forever), Team ($150/mo, with 25% savings on annual billing), and Enterprise (custom pricing). Annual and multi-year contracts available for Enterprise.
- Enterprise services & custom contracts: Enterprise customers negotiate custom MSAs, dedicated deployed engineers, migration services, design services, business associate agreements, and incident response SLAs — sold alongside the platform subscription.
- Freemium / Free tier: Hobby tier is free forever, providing a freemium funnel into paid Team and Enterprise plans. Free trial of 14 days available on the Team tier.
- SDK & CLI generation usage: SDK and CLI Generator capabilities are bundled into the Docs subscription product, sold as part of the platform rather than as a separate SKU. Pricing tiers differ in member counts, AI credits, sites, and feature access.
Pricing tiers
| Model | Billing | Price |
|---|---|---|
| Freemium | Monthly | Hobby: Free forever for individuals getting started |
| Subscription | Monthly | Team: $150/mo for small teams, 25% savings on annual |
| Subscription | Multi-year contract | Enterprise: Custom pricing for scaling teams and enterprises |
Go-to-market motion1 record
Distribution channels5 records
Marketing channels8 records
Fern product offering
Product offeringCore offering
Fern is a docs-as-code platform that generates API documentation websites, idiomatic client SDKs in nine programming languages (TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, Rust), and a branded command-line interface from a single OpenAPI, AsyncAPI, OpenRPC, or gRPC specification. The platform adds AI-native features including Ask Fern (grounded AI chat and search), llms.txt auto-generation, a built-in MCP server, and Fern Writer for AI-assisted documentation authoring.
Product overview
Fern is a single unified platform (developed by Birch Solutions, Inc., a Postman company) that generates API documentation websites (Fern Docs), idiomatic client SDKs in nine programming languages (Fern SDKs), and a branded agent-first CLI (Fern CLI) from one OpenAPI/AsyncAPI/OpenRPC/gRPC source of truth. Around this core the company offers add-on modules: Ask Fern for AI chat and search across docs, Fern Writer for AI-assisted authoring via Slack and Microsoft Teams, Fern Editor for visual in-browser editing, Fern Replay for preserving SDK customizations, and a built-in MCP server for agent integration. Together these products let teams ship a coherent developer and agent experience from a single spec.
Differentiator
Problem solved
Functional benefit
Brands
- Fern Docs: Beautiful, customizable API documentation websites generated from an OpenAPI spec.
- Fern SDKs
- Fern CLI
- Ask Fern
Products and services
- Fern Docs Beautiful, customizable API documentation websites generated from an OpenAPI spec, with docs-as-code workflows, MDX guides, search, analytics, RBAC, SSO, self-hosting, and localization.
- Fern SDKs Generates idiomatic, type-safe client libraries in nine programming languages (TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, Rust) from a single OpenAPI or Fern Definition source, with built-in discriminated unions, auto-pagination, retries, idempotency, OAuth, and unit/mock/integration tests.
- Fern CLI Generates a branded, agent-first command-line interface from an OpenAPI spec with resources as subcommands, JSON output, signed binaries, and distribution to Homebrew, npm, pnpm, Scoop, and a curl installer.
- Ask Fern AI-powered chat and search embedded in Fern Docs that grounds answers in documentation, API references, guides, and SDK code. Available as in-docs chat, a Slack app, a standalone search widget, and a public REST API.
- Fern Writer AI-assisted authoring agent available in Slack and Microsoft Teams that drafts documentation updates and opens GitHub pull requests to keep docs in sync with product changes.
- Fern Editor Browser-based visual editor for non-engineering contributors; every save opens a GitHub pull request so docs-as-code review processes remain intact.
- Fern Replay SDK-generation feature that automatically re-applies manual SDK customizations on top of every regeneration, available across all SDK languages.
- Agent Score Lighthouse-style benchmark that scores a documentation site's AI-agent readiness; Fern applied it publicly to its own docs and shipped the fixes.
Companies that use Fern
Customer profileNamed customers32 records
Segments5 records
Ideal customer profiles4 records
Fern technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- Yes
- API docs
- API detail
Core technology
AI maturity
App detail
Integration13 records
AI capability9 records
Feature9 records
Fern partnerships and signals
Strategic signalPartnerships
Four partnerships are on record, tiered flagship and core.
- PostmanflagshipPostman acquired Fern in January 2026. The entire Fern team joined Postman while maintaining the Fern product, brand, and roadmap unchanged. The acquisition extends Postman's API platform into documentation and SDK generation, gives Fern access to Postman's 500,000+ company network (including 98% of the Fortune 500) and 40M+ developers, and positions Postman as a comprehensive API lifecycle provider from design through consumption. Postman CEO Abhinav Asthana was an early investor in Fern.
- Stainless (alternative SDK generator)coreFern actively markets a 'Migrate from Stainless' landing page (buildwithfern.com/lp/leave-stainless) and published a Stainless-vs-Fern comparison blog post ('Migrate from Stainless today') positioning Fern's 9+ languages, WebSockets, gRPC, CLI workflow, and on-premise deployment against Stainless's dashboard approach. Frame.io evaluated Stainless before selecting Fern.
- Postman Collections integrationcoreFern natively generates and publishes Postman collections from the same OpenAPI source of truth as docs and SDKs, eliminating duplicate specs and manual upkeep. Documented at buildwithfern.com/learn/docs/integrations/postman.
- AI coding agents (Claude Code, Cursor, Microsoft Copilot, ChatGPT, Gemini)coreFern Docs ship an MCP server and llms.txt so that AI coding agents (Anthropic's Claude Code, Cursor, Microsoft Copilot, OpenAI's ChatGPT, Google Gemini) can read live docs and propose accurate changes. Fern Writer is available in Slack and Teams to draft PRs.
Scale indicators9 records
Recent moves6 records
Expansion highlights6 records
Fern competitors and assessment
Company assessmentDirect peers
- Redocly: Redocly provides API documentation and governance tooling built around OpenAPI, with products like Redoc and Reunite. It competes directly with Fern Docs in the API-reference rendering and enterprise docs governance category.
- ReadMe: ReadMe is an established API documentation platform serving enterprise developers. Fern positions itself as the migration destination from ReadMe (with Webflow and Deepgram cited as conversions), making them direct rivals in the enterprise API docs category.
- Mintlify: Mintlify is a direct competitor in API documentation platforms. Fern's case studies explicitly cite customers migrating from Mintlify (ElevenLabs, Payabli), placing the two companies in active head-to-head competition for AI and fintech API teams.
- APIMatic: APIMatic generates SDKs, API documentation, and code samples from API descriptions. It overlaps with Fern on SDK generation and documentation rendering for enterprise API providers.
- Speakeasy: Speakeasy generates production-grade SDKs in multiple languages from OpenAPI specs and bundles Terraform providers and API docs. It targets the same enterprise developer-experience buyer with overlapping core functionality to Fern's SDK and Docs products.
- Stainless: Stainless is a direct competitor offering SDK generation and API documentation tools. Fern actively markets a 'Migrate from Stainless' landing page and Frame.io evaluated Stainless before selecting Fern, indicating tight head-to-head competition in the SDK generator category.
Broad incumbents
- Postman: Postman is Fern's parent company and the dominant API development platform with 500K+ organizations. Although Fern operates as an independent product, Postman's broader API design, testing, and documentation capabilities overlap with Fern's positioning and now own Fern's roadmap direction.
- Swagger (SmartBear) / OpenAPI Generator: Swagger and OpenAPI Generator are the open-source incumbents for API description and SDK generation. Merge's testimonial explicitly cites replacing OpenAPI Generator with Fern, framing this as the dominant legacy alternative that Fern displaces.
- GitBook: GitBook is a broader technical documentation platform used for product, internal, and API docs. It is named by Fern as a competitor and overlaps at the docs-platform layer, though it is not specialized for API-spec-driven generation like Fern.
Emerging players
- Docusaurus (Meta): Docusaurus is an open-source React-based docs framework widely used for API documentation sites. Unleash migrated 300+ pages off Docusaurus to Fern, positioning Docusaurus as the most relevant free, open-source adjacent alternative that Fern targets for displacement.
Market position
Strengths5 records
Weaknesses5 records
Competitive moat6 records
Key risks2 records
Key highlights7 records
Customer concentration
Fern social profiles
Digital presenceFern compliance and trust
Trust signalCompliance1 record
Fern financial estimates
Financial estimateRevenue estimate
Valuation estimate
Fern leadership team
Management profileNumber of profiles
Profiles3 records
Fern funding detail
Funding detailFunding overview
Funding rounds3 records
Investors6 records
Funding detail is available on the Subscription and Enterprise plan.Contact sales →
Fern M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about Fern
What does Fern do?
Fern is a docs-as-code platform that generates API documentation websites, idiomatic client SDKs in nine programming languages (TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, Rust), and a branded command-line interface from a single OpenAPI, AsyncAPI, OpenRPC, or gRPC specification. The platform adds AI-native features including Ask Fern (grounded AI chat and search), llms.txt auto-generation, a built-in MCP server, and Fern Writer for AI-assisted documentation authoring.
Is Fern a public or private company?
Fern is a private company. It is classified as corporate owned and is currently acquired.
When was Fern founded?
Fern was founded in 2022. It employs 51 to 100 people.
Where is Fern based?
Fern is headquartered in New York, United States, in the North America region.
How does Fern make money?
Four revenue lines are on record. Subscription SaaS (Docs product) is the primary driver. The others are enterprise services & custom contracts, freemium / Free tier and SDK & CLI generation usage.
Who are Fern's main competitors?
Direct peers on record are Redocly, ReadMe, Mintlify, APIMatic, Speakeasy and Stainless. Broad incumbents are Postman, Swagger (SmartBear) / OpenAPI Generator and GitBook. Docusaurus (Meta) is listed as an emerging player.
Does Fern have an API?
Yes. Fern exposes a public Ask Fern REST API (developers can build with endpoints for Chat Completion, Document management, Guidance, Code Records, Website indexing, Slack install links, and Query analytics), as well as Fern Writer API endpoints for installing the writing agent. The Fern Docs public API includes endpoints for obtaining JWTs from a Fern API key, retrieving Algolia search credentials, and querying current user information. Authentication is via Fern API keys; auth details, rate limits, and SDK availability are documented under the Public API section of the developer docs. Developer documentation is at buildwithfern.com/learn/docs/fern-api-reference/get-jwt.