Fern

Fern Docs builds interactive documentation websites from Markdown and API specifications, and Fern also generates strongly typed client libraries. It can create API references from OpenAPI, AsyncAPI, gRPC, and other specifications. Documentation features include an API Explorer, web editor, changelog pages, version and product switching, and localization. Generated SDKs include IDE support, schema validation, and idiomatic method names. Fern offers AI search, a writing agent, AI translations, an MCP server, and 250 AI credits per month on its Free plan. That plan is listed as free and includes one site, 10 team members, 1,000 pages, and 2,000 page generations per month. Documentation integrations include PostHog, Google Analytics, Segment, Mixpanel, FullStory, Intercom, Postman, and Context7. Access controls can use password protection, SSO, JWT, or OAuth, with role-based access control. Fern supports custom domains, version history, and content analytics. Its trust center lists SOC 2 Type II, GDPR, and CCPA. Self-hosting is an Enterprise capability.

Fern combines documentation sites, API references, and client library generation with access controls and analytics. The Free plan has defined limits, while self-hosting and dedicated support are listed with Enterprise.

Fern may suit teams publishing API documentation and generating client libraries from API specifications. Its Free plan has stated team, page, generation, and AI-credit limits; Enterprise lists self-hosting, dedicated support, and an uptime SLA.

Fern is a documentation and SDK platform for teams publishing APIs. It suits organizations that want interactive references, generated client libraries, and controlled access in one workflow. The free tier is unusually capable for a single site, but larger or security-sensitive deployments will need Enterprise.

Overview

Fern converts Markdown and API specifications into interactive documentation websites while generating strongly typed client libraries. It supports OpenAPI, AsyncAPI, gRPC, and other specifications, so API teams can keep reference content aligned with their source definitions. IDE support, schema validation, and idiomatic method names make the SDK output more useful to developers than raw generated code.

This focus makes Fern a poor fit for a general-purpose knowledge base with little API content. For product teams whose documentation and SDKs are part of the same developer experience, however, the combined workflow is a persuasive reason to choose it.

Key features

Documentation sites can include an API Explorer, web editor, changelog pages, version and product switching, and localization. Those tools help teams present multiple products and API versions without reducing the site to a static reference dump. A custom domain is supported, and version history provides a way to track published changes.

Fern's AI set includes search, a writing agent, translations, and an MCP server. The Free plan grants 250 AI credits per month, enough for bounded assistance but not an unrestricted content-production workflow. Listed integrations cover PostHog, Google Analytics, Segment, Mixpanel, FullStory, Intercom, Postman, and Context7, giving analytics and developer-tool teams several established connection points.

Access can be restricted with passwords, SSO, JWT, or OAuth, alongside role-based access control. Its trust center identifies SOC 2 Type II, GDPR, and CCPA coverage and provides access requests for security reports and policies. These controls are meaningful for private or partner-facing API documentation, although the more advanced identity and administration features are reserved for Enterprise.

Pricing

Free — free, billed Free forever. This plan allows 10 team members, 1,000 pages, 250 AI credits per month, 2,000 page generations per month, and one site. It is a practical starting point for a small API team or a single product, with clear quotas that constrain large documentation programs and multi-site organizations.

Enterprise — custom pricing. Enterprise adds SSO, SCIM, and advanced RBAC; multiple repositories and documentation instances; advanced analytics and data exports; dedicated infrastructure with self-hosting available; and an uptime SLA with dedicated support. It is the appropriate tier for companies needing centralized identity, multiple deployments, or contractual operational support. The absence of a published price means buyers must budget through a sales process.

Platforms

Fern is offered across web, API, Linux, macOS, and Windows environments, with self-hosting listed for Enterprise. Its CLI generator compiles signed binaries for macOS, Linux, and Windows, which suits engineering teams that want documentation and SDK generation in existing development environments.

Who it's for

Choose Fern for API-first companies publishing references and client libraries together, especially when private documentation, SSO, analytics, or localization matters. The Free plan works for a small team with one site and moderate generation volume. Organizations maintaining several products, requiring self-hosted infrastructure, or needing dedicated support should plan for Enterprise. Teams seeking a broad internal knowledge base without API specifications should look elsewhere.

Pros and cons

• Pro: Documentation and strongly typed SDK generation share one platform, reducing the need to coordinate separate tools.
• Pro: OpenAPI, AsyncAPI, gRPC, and other specification support covers common API publishing workflows.
• Pro: The free tier includes 10 members, 1,000 pages, one site, and substantial monthly generation allowances.
• Pro: Multiple access methods, RBAC, and documented compliance support private developer portals.
• Con: The Free plan is capped at one site, 1,000 pages, and 2,000 page generations per month, limiting larger portfolios.
• Con: Self-hosting, advanced identity, multi-repository operation, enhanced analytics, SLA, and dedicated support require custom-priced Enterprise.
• Con: AI usage is metered at 250 credits per month on Free, so heavy AI-assisted writing will encounter a fixed allowance.

Alternatives

GitBook is a better fit for an individual who wants one free user, unlimited page views, and weekly GitBook Agent messages rather than Fern's API-and-SDK workflow. Choose 0docs when a free, MIT-licensed self-hosted documentation platform is the priority. DocPlatform suits teams wanting a free Community Edition with unlimited editors, workspaces, and pages.

Mintlify is worth choosing for its free five-editor Starter plan with custom domain, authentication, MCP server, and API playground. Sphinx is the straightforward choice for free BSD-licensed software that can be installed locally or self-hosted. Typemill fits teams wanting an extensible core with free plugins, themes, and community support.

Documentation.AI is an alternative for a five-editor starter project with 10,000 one-time AI credits. Docusaurus is the free-for-everyone option for teams that prefer a self-hosted documentation site without a subscription model.

For broader comparisons, see Developer Documentation Software, Technical Documentation Software, AI Documentation Generators, Code Generators, API Documentation Tools, and Knowledge base software.

Verdict

Fern is a strong recommendation for API teams that want interactive documentation and maintained client libraries from the same source. Its generous single-site Free plan lowers the barrier to adoption, while access controls and analytics support serious developer portals. Look elsewhere if you need a general knowledge base, unlimited free sites, or self-hosting and enterprise administration without custom pricing.