Fern
Docs, SDKs, and a CLI for your API, built for the AI era.
Fern is a developer experience platform that turns an API specification into client SDKs, interactive documentation, and a CLI from a single source of truth. It supports REST, WebSockets, GraphQL, and other protocols, and includes features designed for both developers and AI agents. The platform aims to keep documentation, generated libraries, and terminal tooling in sync as an API evolves.
Fern's main capabilities include customizable documentation websites, client libraries generated for multiple languages, and a CLI for interacting with an API from the terminal. It supports specifications such as OpenAPI, AsyncAPI, gRPC, GraphQL, and OpenRPC. AI-oriented features include built-in AI chat grounded in documentation, AI search, AI-assisted authoring through Fern Agent, an MCP server, llms.txt generation, and AI translations. Additional features cover docs-as-code workflows, API Explorer, Postman collection generation, localization, multi-source docs aggregation, visitor authentication, RBAC, SSO, and self-hosting.
Fern is aimed at development teams and organizations that maintain API documentation and SDKs, including those with governance, scale, and security requirements. Pricing is offered in a Free plan with a limited number of team members, pages, and monthly AI credits, and an Enterprise edition with custom terms. Enterprise features include SSO, SCIM, advanced RBAC, multiple repos and docs instances, custom design integration, advanced analytics, dedicated infrastructure, self-hosting, uptime SLAs, and dedicated support. A separate Postman Customer offering is available with a free tier and an Enterprise edition.
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