Fern is a developer-tools platform that turns a single API specification into idiomatic client SDKs, beautiful API documentation, and MCP servers. Given OpenAPI, AsyncAPI, gRPC/Protobuf, or Fern's own Fern Definition as input, Fern generates type-safe SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust, publishes them to registries like npm, PyPI, and Maven, and builds a hosted docs site with an interactive API reference, API playground, and an AI-powered "Ask Fern" search. The primary interface is the open-source `fern` CLI (Apache-2.0, github.com/fern-api/fern) driving a hosted platform - the fern-api catalog documents Fern's SDK-generation, documentation-generation, and Fern Definition capability surfaces as capability areas, plus the one hosted public REST API Fern exposes to customers, the Ask Fern API. Fern is open-core: the CLI and generators are open source, and Docs and SDKs are sold on Hobby (free), Team, and Enterprise plans.
Fern publishes 2 APIs on the APIs.io network: Ask API and Website Sources API. Tagged areas include API Lifecycle, SDK Generation, Client Library, API Documentation, and Developer Tools.
Fern’s developer surface includes authentication, documentation, engineering blog, and 7 more developer resources.
Capability area (CLI/platform, not a hosted REST API) that generates idiomatic, type-safe client SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust from OpenAP...
Capability area (CLI/platform) that builds a hosted documentation website with a generated API reference, interactive API playground, changelogs, versioning, keyword search, and...
aid: fern-api
url: https://raw.githubusercontent.com/api-evangelist/fern-api/refs/heads/main/apis.yml
name: Fern
kind: company
description: 'Fern is a developer-tools platform that turns a single API specification into idiomatic client SDKs, beautiful
API documentation, and MCP servers. Given OpenAPI, AsyncAPI, gRPC/Protobuf, or Fern''s own Fern Definition as input, Fern
generates type-safe SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust, publishes them to registries like
npm, PyPI, and Maven, and builds a hosted docs site with an interactive API reference, API playground, and an AI-powered
"Ask Fern" search. The primary interface is the open-source `fern` CLI (Apache-2.0, github.com/fern-api/fern) driving a
hosted platform - the fern-api catalog documents Fern''s SDK-generation, documentation-generation, and Fern Definition capability
surfaces as capability areas, plus the one hosted public REST API Fern exposes to customers, the Ask Fern API. Fern is open-core:
the CLI and generators are open source, and Docs and SDKs are sold on Hobby (free), Team, and Enterprise plans.'
accessModel:
pricing: freemium
onboarding: self-serve
trial: false
try_now: true
public: false
label: Freemium · Self-serve signup
confidence: high
source:
- plans
- authentication
generated: '2026-07-22'
method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/fern-api.png
tags:
- API Lifecycle
- SDK Generation
- Client Library
- API Documentation
- Developer Tools
- OpenAPI
- CLI
- Open Source
- Developer Experience
created: '2026-07-11'
modified: '2026-07-11'
specificationVersion: '0.19'
apis:
- aid: fern-api:fern-api-sdk-generation
name: Fern SDK Generation
tags:
- SDK Generation
- Client Library
- Developer Tools
- API Lifecycle
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
humanURL: https://buildwithfern.com/learn/sdks/overview
properties:
- url: https://buildwithfern.com/learn/sdks/overview
type: Documentation
- url: https://buildwithfern.com/learn/cli-api-reference/cli-reference/commands
type: APIReference
- url: https://github.com/fern-api/fern
type: SourceCode
description: Capability area (CLI/platform, not a hosted REST API) that generates idiomatic, type-safe client SDKs in TypeScript,
Python, Go, Java, C#, PHP, Ruby, Swift, and Rust from OpenAPI, AsyncAPI, gRPC, or Fern Definition input. Driven by `fern
generate`; SDKs are published to GitHub and registries (npm, PyPI, Maven). Endpoints are modeled from the CLI surface
rather than a public REST API.
- aid: fern-api:fern-api-documentation
name: Fern API Documentation
tags:
- API Documentation
- Developer Portal
- Docs as Code
- Developer Experience
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
humanURL: https://buildwithfern.com/learn/docs/getting-started/overview
properties:
- url: https://buildwithfern.com/learn/docs/getting-started/overview
type: Documentation
- url: https://buildwithfern.com/learn/docs/api-references/generate-api-ref
type: APIReference
- url: https://github.com/fern-api/fern
type: SourceCode
description: Capability area (CLI/platform) that builds a hosted documentation website with a generated API reference, interactive
API playground, changelogs, versioning, keyword search, and docs-as-code (Markdown + git) authoring. Driven by `fern generate
--docs` and `fern docs dev`. Endpoints are modeled from the CLI and platform surface rather than a public REST API.
- aid: fern-api:fern-api-definition-cli
name: Fern Definition and CLI
tags:
- CLI
- API Design
- API Lifecycle
- Developer Tools
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
humanURL: https://buildwithfern.com/learn/cli-api-reference/cli-reference/commands
properties:
- url: https://buildwithfern.com/learn/cli-api-reference/cli-reference/commands
type: Documentation
- url: https://buildwithfern.com/learn/api-definitions/openapi/authentication
type: APIReference
- url: https://github.com/fern-api/fern
type: SourceCode
description: Capability area covering Fern's open-source (Apache-2.0) command-line interface and the proprietary Fern Definition
API-description format. Core commands include `fern init`, `fern check`, `fern generate`, `fern login`, `fern token`,
`fern export`, and `fern docs dev`. Endpoints are modeled from the CLI surface, not a hosted REST API.
- aid: fern-api:fern-api-ask-api
name: Fern Ask API
description: Query indexed documentation for AI-generated, grounded answers.
humanURL: https://buildwithfern.com/learn/sdks/overview
baseURL: https://fai.buildwithfern.com
tags:
- Ask
properties:
- type: OpenAPI
url: openapi/fern-api-ask-api-openapi.yml
- type: Documentation
url: https://buildwithfern.com/learn/docs/ai-features/ask-fern/api-reference/overview
- type: APIReference
url: https://buildwithfern.com/learn/docs/ai-features/ask-fern/api-reference/website/get-website-status
- type: PostmanCollection
url: collections/fern-api.postman_collection.json
- type: OpenCollection
url: collections/fern-api.opencollection.json
- aid: fern-api:fern-api-website-sources-api
name: Fern Website Sources API
description: Index documentation websites and check indexing job status.
humanURL: https://buildwithfern.com/learn/sdks/overview
baseURL: https://fai.buildwithfern.com
tags:
- Website Sources
properties:
- type: OpenAPI
url: openapi/fern-api-website-sources-api-openapi.yml
- type: Documentation
url: https://buildwithfern.com/learn/docs/ai-features/ask-fern/api-reference/overview
- type: APIReference
url: https://buildwithfern.com/learn/docs/ai-features/ask-fern/api-reference/website/get-website-status
- type: PostmanCollection
url: collections/fern-api.postman_collection.json
- type: OpenCollection
url: collections/fern-api.opencollection.json
common:
- type: AgenticAccess
url: agentic-access/fern-api-agentic-access.yml
- type: Authentication
url: authentication/fern-api-authentication.yml
- type: GitHubOrganization
url: https://github.com/fern-api
- type: LinkedIn
url: https://www.linkedin.com/company/buildwithfern
- type: Website
url: https://buildwithfern.com
- type: Documentation
url: https://buildwithfern.com/learn/home
- type: Plans
url: plans/fern-api-plans-pricing.yml
- type: RateLimits
url: rate-limits/fern-api-rate-limits.yml
- type: FinOps
url: finops/fern-api-finops.yml
- url: https://buildwithfern.com/blog
type: Blog
maintainers:
- FN: Kin Lane
email: kin@apievangelist.com
ⓘWhere this information came from
This is an independent, third-party profile of Fern, published by
API Evangelist. We do not operate, host, resell, or
support these APIs, and we are not affiliated with or endorsed by the company unless stated above.
Everything here is built from publicly available information — the company's own site,
developer portal, documentation, public repositories, and the specifications it publishes for public use.
Nothing is obtained by breaching a system, defeating an access control, or using credentials.
The Kin Score and Agent Readiness rating are independently calculated assessments of a company's
public API artifacts, scored against a published rubric. They are not certifications,
endorsements, security assessments, or audits.
Corrections, re-scores, and removal are free — no partnership or purchase required, and
you do not need to justify the request. A removed company is recorded as unrated, never scored
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