> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.getunleash.io/api/frontend-api-overview/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.getunleash.io/_mcp/server.

# Frontend API overview

> The Frontend API is used by frontend SDKs to fetch enabled feature flags for a specific Unleash Context.

The Frontend API is designed for [frontend SDKs](/sdks/react) running in browsers, mobile apps, and other client-side environments. Unlike the [Client API](/api), it only returns enabled feature flags for a specific [Unleash Context](/concepts/unleash-context), providing security and performance benefits.

**Base path**: `<your-unleash-url>/api/frontend`

**Primary use**: Fetch enabled flags for a specific user context without exposing your entire flag configuration. Frontend SDKs handle registration, polling, and metrics automatically.

## Key differences from Client API

| Aspect         | [Client API](/api)                                                                              | Frontend API                                                                    |
| -------------- | ----------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------- |
| **Payload**    | All [feature flags](/concepts/feature-flags) and [strategies](/concepts/activation-strategies). | Only enabled [feature flags](/concepts/feature-flags) for the provided context. |
| **Evaluation** | Server-side by SDK.                                                                             | Evaluated by the Unleash server or [Unleash Enterprise Edge](/unleash-edge).    |
| **Token type** | [Backend tokens](/concepts/api-tokens-and-client-keys#backend-tokens).                          | [Frontend tokens](/concepts/api-tokens-and-client-keys#frontend-tokens).        |

## Authentication

Use **[frontend tokens](/concepts/api-tokens-and-client-keys)** for authentication. These tokens can be scoped to specific [projects](/concepts/projects) and [environments](/concepts/environments) and are safe to embed in client-side code.

To create a frontend token, go to **Admin settings > Access control > API access > New API token**.

## Available endpoints

| Endpoint                        | Method | Description                                                                  |
| ------------------------------- | ------ | ---------------------------------------------------------------------------- |
| `/api/frontend`                 | GET    | Fetch enabled [feature flags](/concepts/feature-flags) (using query params). |
| `/api/frontend`                 | POST   | Fetch enabled [feature flags](/concepts/feature-flags) (using request body). |
| `/api/frontend/client/metrics`  | POST   | Report usage [metrics](/concepts/impression-data).                           |
| `/api/frontend/client/register` | POST   | Register [SDK](/sdks) instance.                                              |

## Unleash Context

Each request requires an [Unleash Context](/concepts/unleash-context) to evaluate flags. For example, include fields like `userId`, `sessionId`, and custom `properties` for targeting:

```json
{
  "userId": "user-123",
  "properties": {
    "region": "us-east",
    "plan": "premium"
  }
}
```

Learn more about [context fields and constraints](/concepts/unleash-context).

## Using with Unleash Edge

For production applications, use [Unleash Edge](/unleash-edge) to improve performance, privacy, and reduce latency. Edge caches evaluations closer to your users and provides built-in fallback mechanisms.

Point your SDK to your Edge instance instead of directly to Unleash:

```javascript
const config = {
  url: 'https://your-edge-instance.com/api/frontend',
  clientKey: 'YOUR_FRONTEND_TOKEN',
};
```

> The Frontend API is used by frontend SDKs to fetch enabled feature flags for a specific Unleash Context.