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Fern

buildwithfern.com

Free plan Open source WebWindowsmacOSLinuxAPISelf-hosted
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Spec score 8.9 #1 of 27 in API Documentation Tools

Spec sheet

What it does
Fern turns API definitions and Markdown into hosted documentation sites, SDKs, and command-line tools.Read 14 Oct 2026 · buildwithfern.com
Publishing audience
bothRead 20 Sep 2026 · buildwithfern.com
Free plan
YesRead 20 Sep 2026 · buildwithfern.com
Integrations
Listed integrations include PostHog, Google Analytics, Segment, Mixpanel, FullStory, Intercom, Postman, and Context7.Read 5 Oct 2026 · buildwithfern.com
Security
Fern's trust center lists SOC 2 Type II, GDPR, and CCPA and provides access requests for its SOC 2 report, penetration test summary, and information security policy.Read 5 Oct 2026 · buildwithfern.com
Compliance
Fern's trust center lists SOC 2 Type II, GDPR, and CCPA, with a SOC 2 report and penetration-test summary available by request.Read 14 Oct 2026 · buildwithfern.com
Support
The Enterprise plan includes dedicated support and an uptime SLA.Read 5 Oct 2026 · buildwithfern.com
Company
Fern identifies itself as Birch Solutions, Inc., a Postman company, and says it was born in Brooklyn, New York.Read 5 Oct 2026 · buildwithfern.com
Access control
Fern supports documentation access through password protection, SSO, JWT, or OAuth, with role-based access control.Read 5 Oct 2026 · buildwithfern.com
Accessibility
Fern documents WCAG 2.1 AA contrast, keyboard navigation, and screen-reader support for documentation sites.Read 14 Oct 2026 · buildwithfern.com
Acquisition continuity
Fern said it would continue operating as an independent product after joining Postman, with its product, brand, and roadmap unchanged.Read 14 Oct 2026 · buildwithfern.com
Acquisition news
Postman announced its acquisition of Fern on January 8, 2026; Postman said Fern had a 25-person team and more than 200 customers at that time.Read 14 Oct 2026 · blog.postman.com
AI features
Ask Fern answers documentation questions with citations, while Fern Agent can propose documentation changes as pull requests.Read 14 Oct 2026 · buildwithfern.com
AI tools
Fern offers AI search, a writing agent, AI translations, an MCP server, and 250 AI credits on the Free plan.Read 5 Oct 2026 · buildwithfern.com
API Explorer
Published documentation can include an API Explorer that sends real requests with prefilled authentication.Read 14 Oct 2026 · buildwithfern.com
API references
Fern generates interactive API references from OpenAPI, AsyncAPI, gRPC, GraphQL, OpenRPC, and related specifications.Read 14 Oct 2026 · buildwithfern.com
CLI platforms
Fern says its CLI generator compiles signed binaries for macOS, Linux, and Windows.Read 5 Oct 2026 · buildwithfern.com
CLI requirements
The current CLI installation documentation requires Node.js 22 or newer and supports npm or Homebrew installation.Read 14 Oct 2026 · buildwithfern.com
Company facts
LinkedIn lists Fern as founded in 2022, headquartered in Brooklyn, New York, privately held, and employing 11–50 people.Read 14 Oct 2026 · linkedin.com
Company identity
Fern's legal entity is Birch Solutions, Inc., and its current parent is Postman.Read 14 Oct 2026 · marketing.postman-stage.com
Content analytics
YesRead 20 Sep 2026 · buildwithfern.com
Current CLI release
The CLI changelog lists version 5.157.2 on October 14, 2026, including a fix for OpenAPI tag section naming.Read 14 Oct 2026 · buildwithfern.com
Custom domain
YesRead 20 Sep 2026 · buildwithfern.com
Custom integrations
Enterprise customers can add unsupported analytics, support, session-recording, and tag-management tools through custom JavaScript.Read 14 Oct 2026 · buildwithfern.com
Documentation
Fern Docs builds interactive documentation websites from Markdown and API specifications.Read 5 Oct 2026 · buildwithfern.com
Documentation authoring
Docs can be edited through GitHub pull requests, an in-browser Fern Editor, an IDE, Slack, or Fern Agent.Read 14 Oct 2026 · site.buildwithfern.com
Documentation features
Docs features include an API Explorer, web editor, changelog pages, version and product switching, and localization.Read 5 Oct 2026 · buildwithfern.com
Free plan limits
The Free plan includes 10 team members, 1,000 pages, 250 AI credits per month, and 2,000 page generations per month.Read 5 Oct 2026 · buildwithfern.com
Independent assessment: Thoughtworks
Thoughtworks reported positive initial impressions because Fern reduces documentation toil, while criticizing the need for proprietary configuration despite OpenAPI conversion support.Read 14 Oct 2026 · thoughtworks.com
Independent score
Documentation.AI scored Fern 3.8 out of 5 overall, with API reference and explorer capabilities receiving its strongest score at 4.7.Read 14 Oct 2026 · documentation.ai
Independent score: MakerStack
MakerStack rated Fern 7.6 out of 10 and described its SDK output and documentation synchronization as strengths.Read 14 Oct 2026 · makerstack.co
Limit: Documentation.AI preview
The review reports that local preview can be slow, needs Node 22 and pnpm, and Windows installations may fail on sharp or esbuild without a WSL workaround.Read 14 Oct 2026 · documentation.ai
Limit: Documentation.AI pricing
The review says pricing becomes an Enterprise quote when a team exceeds 10 editors, needs a second site, custom CSS, or reader SSO, and that AI credits cannot be purchased separately.Read 14 Oct 2026 · documentation.ai
Limit: Documentation.AI SDKs
The review reports language-specific defects in generated SDKs and estimates they represented about one fifth of its issue tracker during testing.Read 14 Oct 2026 · documentation.ai
Limit: MakerStack
MakerStack criticized opaque cloud pricing, vendor lock-in from Fern Definition, and manual work required for advanced webhook or streaming patterns.Read 14 Oct 2026 · makerstack.co
Local generation requirements
Local CLI generation requires Docker, a Fern token, and a stable Rust toolchain in addition to the CLI.Read 14 Oct 2026 · buildwithfern.com
MCP
Each Fern documentation site can expose an MCP server for coding agents and AI tools.Read 14 Oct 2026 · site.buildwithfern.com
Notable changelog
The documentation changelog records Fern Agent and a private MCP server on August 25, 2026, and readable API-reference Markdown for agents on August 10, 2026.Read 14 Oct 2026 · buildwithfern.com
Open-source licence
The public Fern repository is marked Apache-2.0; Fern describes its Docs and SDK Generator products as open source, while the hosted service remains commercial.Read 14 Oct 2026 · github.com
Open-source status caveat
The GitHub repository warns that the project is no longer maintained and directs users toward hosted Fern services.Read 14 Oct 2026 · github.com
Praise: Documentation.AI
The independent review praised the unified workflow for generating documentation, SDKs, and a CLI from one API definition, plus a generous free tier.Read 14 Oct 2026 · documentation.ai
Praise: G2 reviewer
The verified G2 reviewer praised quick API-request testing inside Fern and the responsiveness of Fern's team.Read 14 Oct 2026 · g2.com
Public API
Fern exposes a REST API for Ask Fern configuration, custom context and FAQs, usage, and analytics, authenticated with organization API keys.Read 14 Oct 2026 · buildwithfern.com
Rating on G2
5.0 out of 5 from 1 review.Read 14 Oct 2026 · g2.com
SDK behavior
Generated SDKs include strong typing, pagination helpers, retries with backoff, idempotency headers, multipart uploads, and discriminated unions.Read 14 Oct 2026 · site.buildwithfern.com
SDK extensibility
Teams can add custom code, merge multiple API definitions, and automatically publish packages to registries such as npm, PyPI, and Maven.Read 14 Oct 2026 · buildwithfern.com
SDK generation
Fern generates strongly typed client libraries with IDE support, schema validation, and idiomatic method names.Read 5 Oct 2026 · buildwithfern.com
SDK languages
SDK generation supports TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust.Read 14 Oct 2026 · buildwithfern.com
Security architecture
Fern says authentication credentials are kept in browser cookies and are not transmitted to Fern servers in its client-side security model.Read 14 Oct 2026 · buildwithfern.com
Self-hosted docs
Enterprise users can deploy a private Docker image that renders documentation to static HTML on their own infrastructure, including air-gapped environments.Read 14 Oct 2026 · buildwithfern.com
Self-hosted SDK generation
SDK generation can run locally or on customer infrastructure with Docker; the API specification remains outside Fern infrastructure except for organization verification and image retrieval.Read 14 Oct 2026 · buildwithfern.com
Self-hosting
Fern lists self-hosting as an Enterprise capability for deploying on dedicated infrastructure.Read 5 Oct 2026 · buildwithfern.com
Self-hosting limitation
Self-hosted documentation does not include some hosted features, including Ask Fern and analytics.Read 14 Oct 2026 · buildwithfern.com
SSO support
YesRead 20 Sep 2026 · buildwithfern.com
Supported integrations
Native integrations include PostHog, Google Analytics, Segment, Mixpanel, FullStory, Intercom, Postman, and Context7.Read 14 Oct 2026 · buildwithfern.com
Supported specifications
Fern Docs generates API references from OpenAPI, AsyncAPI, gRPC, and other specifications.Read 5 Oct 2026 · buildwithfern.com
Version history
YesRead 20 Sep 2026 · buildwithfern.com

Plans and prices

Free Free Free forever; $0/mo 10 team members · 1,000 pages · 250 AI credits/month · 2,000 page generations/month · 1 site · custom domain/subpath · API Explorer · web editor · Ask Fern · Fern Agent · MCP server · version/product switching Read 14 Oct 2026 · buildwithfern.com
Enterprise Priced on request Tailored pricing terms Everything in Free · SSO/SCIM/advanced RBAC · multiple repositories and docs instances · custom CSS/JavaScript/React · custom layouts · advanced analytics/data exports · dedicated infrastructure · self-hosting · uptime SLA · dedicated support Read 14 Oct 2026 · buildwithfern.com

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