# SDKs

Generate idiomatic SDKs from your OpenAPI spec.

## Languages

Fern generates SDKs in 9 languages from a single API specification:

- TypeScript / JavaScript
- Python
- Go
- Java
- C# / .NET
- Ruby
- PHP
- Swift
- Rust

Each SDK is hand-tuned per language, not a thin wrapper. Generated code follows the idioms developers expect: typed responses, language-native error handling, async support, and standard package layouts.

## What Fern SDKs include

- **Strongly typed clients.** Request and response types generated from your spec.
- **Pagination helpers.** Cursor-based and offset-based pagination are first-class.
- **Retries with backoff.** Configurable retry policy for transient failures.
- **OAuth and bearer auth.** Token refresh handled automatically where the spec describes it.
- **File upload and streaming.** Multipart uploads and SSE/streaming responses supported.
- **Forward compatibility.** Unknown fields are preserved, deprecations surface as warnings, and additive spec changes don't break old clients.
- **Idempotency.** Idempotency keys threaded through where the spec marks them.

## Workflow

1. Point Fern at your OpenAPI spec.
2. Configure language-specific options (package name, namespace, version) in fern.yaml.
3. Run `fern generate` to produce SDKs in your selected languages.
4. Fern publishes to npm, PyPI, Maven Central, NuGet, RubyGems, Packagist, CocoaPods, and crates.io.
5. Every spec change regenerates the SDKs — no manual edits, no drift.

## Customizations

- Add custom helper methods (auth bootstrap, common workflows) without forking the generator.
- Override naming, grouping, or error mapping per-language via configuration.
- Bring your own changelog and release notes pipeline.

## Trusted by

NVIDIA, Adobe, ElevenLabs, Twilio, Cohere, OpenRouter, Square.

## Next steps

- Book a demo: <https://buildwithfern.com/book-demo>
- See pricing: <https://buildwithfern.com/pricing>
- Read customer stories: <https://buildwithfern.com/customers>