tools
Fern SDK Generator
Fern generates typed client SDKs from API specifications, adds tests and custom code, and publishes packages for multiple programming languages.

In inglese
Fern turns OpenAPI, AsyncAPI, OpenRPC, gRPC, or Fern Definition files into client libraries for TypeScript, Python, Go, Java, Ruby, C#, PHP, Swift, and Rust. It can generate SDK code in the cloud or locally, add package metadata, run tests, and publish packages to registries such as npm, PyPI, and Maven.
Teams use it to maintain SDKs alongside evolving APIs. The generated libraries include typed models, pagination, retries, authentication helpers, webhook verification, documentation, and code samples. The pricing page lists Free and Enterprise plans; enterprise features include self-hosting, advanced access controls, and dedicated support.
Features
- Generate SDKs from OpenAPI, AsyncAPI, OpenRPC, gRPC, or Fern Definition files
- Support TypeScript, Python, Go, Java, Ruby, C#, PHP, Swift, and Rust
- Generate strongly typed models, methods, documentation, and code snippets
- Add custom code that survives SDK regeneration
- Generate pagination, retries, idempotency, multipart uploads, SSE, and WebSocket support
- Generate unit, mock-server, wire, and integration tests
- Publish packages to registries including npm, PyPI, and Maven
- Run generation in Fern Cloud or on your own infrastructure
Use cases
- Generate client libraries for a public API
- Publish SDK updates when an API specification changes
- Create consistent SDKs across several programming languages
- Add custom helpers without losing them during regeneration
- Test generated clients against mock servers and live APIs
- Publish versioned packages to language-specific registries
Pros
Cons
Latest updates
- 3.96.3 (3.96.3)
The matcher now ignores a parent object absent from the expected body when every leaf inside it is an ignored field.
- 3.96.2 (3.96.2)
The generated OAuth wire-test mock now expects the grant_type the generated OAuthAuthProvider actually sends.
- 3.96.1 (3.96.1)
Bump bundled @fern-api/generator-cli to 0.10.1; when AI analysis returns an empty changelog entry, the PR description, version bump reason, or commit message body is…
- 3.96.0 (3.96.0)
Object types with XML encoding metadata are generated as classes with toXml(), a static fromXml() parser, and a fluent Builder.
- 3.95.1 (3.95.1)
Dynamic snippets honor flattenRequestParameters and nest multi-auth constructor options under the camelCase auth scheme key.
Capabilities
- Runs commands — “CLI Interact with your API from the terminal.” source
- Command line — “CLI Interact with your API from the terminal.” source
- Self-hosted — “Self-host Run on our managed cloud, or self-host to meet stricter security, networking, and compliance requirements.” source
- Official SDKs — “We support TypeScript, Python, Go, Java, Ruby, C#, PHP, Swift & Rust.” source
Get it
Security
Pricing
- Starting price
- Free
- Prices checked
- 2026-09-24
Free
Free
- 10 team members
- 1,000 pages
- 250 AI credits per month
- 2,000 page generations per month
- Custom domain and subpath
- Guides, API references, and changelogs
Enterprise
Price on request
- Everything in Free, plus:
- SSO, SCIM, and advanced RBAC
- Multiple repos and docs instances
- Custom CSS, JavaScript, and React components
- Custom layouts and design-system integration
- Advanced analytics and data exports