Fern

Fern is a platform that automatically generates SDKs and API documentation from your API definition. You provide your OpenAPI, AsyncAPI, or gRPC specification, and Fern creates ready-to-use client libraries in languages like TypeScript, Python, Go, Java, Ruby, C#, PHP, and Swift.

The platform also builds documentation websites that look professional and match your brand identity. These sites include interactive API references, code examples, and a playground where developers can test your API without leaving the documentation.

Fern is open source and available on GitHub. It integrates with your existing workflow by publishing SDKs directly to package registries like npm and PyPI. The tool is designed for companies that want to provide a great developer experience without dedicating engineering resources to manual SDK maintenance.

Getting started with Fern is straightforward. Here's how to use it:

• Install the Fern CLI using npm by running the installation command in your terminal. You'll need Node.js version 18 or higher.

• Initialize a Fern project by running the init command with your OpenAPI specification. You can use a local file or provide a URL to your API specification.

• Configure which outputs you want in the generators file. You can choose to generate SDKs in multiple languages, create documentation, or both.

• Run the generate command to create your SDKs and documentation. Fern processes your API definition and outputs the requested artifacts.

• Customize your documentation by adding markdown pages, adjusting colors and fonts, and setting up your custom domain.

• Set up automatic publishing so Fern can push your SDKs to package registries and update your documentation site whenever you make API changes.

• Automatic SDK generation in 8+ programming languages

• Stripe-style API documentation websites

• Direct publishing to package registries

• OpenAPI and AsyncAPI support

• Interactive API playground with live testing

• Custom branding and domain support

• Built-in OAuth 2.0 and authentication

• Automatic pagination and retry logic

• WebSocket and SSE support

• Version control with Git

• AI-powered search assistant

• Open source on GitHub