***

title: API Explorer
subtitle: >-
Reduce "time to 200" by allowing users to make real calls to your API from
right within the API Reference.
-------------------------------

Fern's API Explorer allows users to make authenticated requests to your API without ever leaving your documentation.

## Autopopulate with examples

Fern will automatically populate the fields of the endpoint with the values set in your API specification.

<div>
  <iframe src="https://www.loom.com/embed/a48d921459b54dde9652c3fcc85ebc54?sid=2c0b4f4d-7e24-4fc5-a617-8d933195bfec?hide_owner=true&hide_share=true&hide_title=true&hideEmbedTopBar=true" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen />
</div>

## Authentication

The API Explorer supports [all authentication schemes](/learn/api-definitions/openapi/authentication) configured in your OpenAPI spec or in `generators.yml`, including multiple authentication schemes. When multiple schemes are available, the API Explorer automatically displays them in a dropdown menu, allowing users to select and configure their preferred authentication method before sending requests.

Once a user sets their authentication credentials, their credentials persist throughout their entire exploration session.

<div>
  <iframe src="https://www.loom.com/embed/7de9948ae878448094b5e92da5effd41?sid=702889b7-aa3d-4669-994e-83c196d7bc3e?hide_owner=true&hide_share=true&hide_title=true&hideEmbedTopBar=true" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen />
</div>

<Info>
  Authentication credentials are only stored client-side using cookies. No sensitive user information is collected or stored.
</Info>

To automatically populate API keys for logged-in users, see [API key injection](/learn/docs/authentication/features/api-key-injection).

## Multiple environments

When multiple server URLs are configured in [OpenAPI](/learn/api-definitions/openapi/extensions/server-names) or the [Fern Definition](/learn/api-definition/fern/api-yml/environments), users can switch between environments (e.g., production and sandbox) from a dropdown in the API Explorer. The selected environment persists as they navigate between pages.

<div>
  <iframe src="https://www.loom.com/embed/cb642161678e41cabcb677b900006f40?sid=5e45243c-3ba1-45cf-860b-72eee1970fc5?hide_owner=true&hide_share=true&hide_title=true&hideEmbedTopBar=true" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen />
</div>

Users can also double-click the server URL to manually edit it, allowing for quick testing against custom environments or endpoints.

Here's an example of the [Flagright docs site](https://docs.flagright.com/framl-api/api-reference/api-reference/transactions/get) with multiple server names configured.

<Tabs>
  <Tab title="OpenAPI">
    <CodeBlock>
      ```yaml
      openapi: 3.0.0
      servers:
        - url: https://sandbox.api.flagright.com
          x-fern-server-name: Sandbox API server (eu-1)
        - url: https://sandbox-asia-1.api.flagright.com
          x-fern-server-name: Sandbox API server (asia-1)
      ```
    </CodeBlock>
  </Tab>

  <Tab title="Fern Definition">
    <CodeBlock>
      ```yaml
      environments:
        Sandbox API server (eu-1): https://sandbox.api.flagright.com
        Sandbox API server (asia-1): https://sandbox-asia-1.api.flagright.com
      ```
    </CodeBlock>
  </Tab>
</Tabs>

## WebSocket Playground

For APIs that support WebSocket connections, the API Explorer includes a **WebSocket**-specific Playground. The WebSocket Playground also allows users to establish a connection with the API, and send/receive messages in real-time.

<div>
  <iframe src="https://www.loom.com/embed/be4da30404794e9983c4fe639f78d4c8?sid=73b7aeda-98fa-4531-87ed-1e5909500fe2?hide_owner=true&hide_share=true&hide_title=true&hideEmbedTopBar=true" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen />
</div>

## Control API Explorer availability

For OpenAPI specs, the API Explorer is enabled by default for all endpoints. You can disable it globally or per endpoint using the [`x-fern-explorer`](/learn/api-definitions/openapi/extensions/api-explorer-control) extension. This is commonly used to disable the Explorer for destructive operations, payment processing, or admin-only endpoints.