# API reference

> Interactive documentation generated from your API specification

Fern automatically generates interactive API reference documentation from your API specification. This starter template includes a sample Plant Store API to demonstrate the feature.

## Supported specifications

Fern supports multiple API specification formats:

| Format       | Description                                                                     | Documentation                                                                    |
| ------------ | ------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- |
| **OpenAPI**  | The most widely used REST API specification format (versions 2.0, 3.0, and 3.1) | [OpenAPI docs](https://buildwithfern.com/learn/api-definitions/openapi/overview) |
| **AsyncAPI** | For event-driven and message-based APIs                                         | [AsyncAPI docs](https://buildwithfern.com/learn/api-definitions/asyncapi)        |
| **gRPC**     | Protocol buffer definitions for gRPC services                                   | [gRPC docs](https://buildwithfern.com/learn/api-definitions/protobuf)            |

## How it works

Place your API specification file in the `fern/` directory and reference it in your `docs.yml` navigation:

```yaml title="docs.yml"
navigation:
  - section: Documentation
    contents:
      - page: Overview
        path: docs/pages/overview.mdx
  - api: API Reference
```

Fern parses your specification and generates:

* Endpoint documentation with request/response schemas
* Interactive API Explorer for testing endpoints
* Code snippets in multiple languages
* Type definitions and examples

## API Explorer

The API Explorer lets users test API endpoints directly in the documentation. Users can fill in parameters, send requests, and see responses without leaving the page.

<Note>
  For advanced API Explorer features like auto-populating API keys, see the [API Explorer documentation](https://buildwithfern.com/learn/docs/api-references/api-explorer/overview).
</Note>

## Customizing the API reference

Control how your API reference appears using the `api` configuration in `docs.yml`:

```yaml title="docs.yml"
navigation:
  - api: API Reference
    api-name: plantstore
    paginated: true
```

You can also add custom content to API reference pages, organize endpoints into groups, customize section names, and control which endpoints are visible.

<Note>
  For detailed customization options, see the [API reference documentation](https://buildwithfern.com/learn/docs/api-references/generate-api-ref).
</Note>

## SDK code snippets

If you generate SDKs with Fern, code snippets automatically appear in your API reference showing how to call each endpoint using your SDK:

```yaml title="generators.yml"
groups:
  python-sdk:
    generators:
      - name: fernapi/fern-python-sdk
        version: 4.3.1
        output:
          location: pypi
          package-name: plantstore
```

<Note>
  For more information on SDK generation, see the [SDK documentation](https://buildwithfern.com/learn/sdks/overview/introduction).
</Note>