> ## Documentation Index
> Fetch the complete documentation index at: https://prostack.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication API

> API endpoints for user authentication

ProStack uses Better-Auth to provide a comprehensive authentication system. The authentication API handles user registration, login, session management, and integration with Polar for subscription management.

## Authentication Flow

All authentication endpoints are managed by Better-Auth and are available under the `/api/auth` path. The authentication system supports:

* Email/password authentication
* Social login (Google)
* Password reset
* Team/organization management
* Subscription and billing integration with Polar

## Polar Subscription Endpoints

ProStack integrates with Polar for subscription and billing management. The following endpoints are available for authenticated users:

### Checkout a Product/Plan

<CodeGroup>
  ```bash Request theme={null}
  GET /api/auth/checkout/{product-slug}
  ```

  ```text Response theme={null}
  // Redirects to Polar checkout page for the specified product
  ```
</CodeGroup>

This endpoint initiates the checkout process for a subscription plan. The user must be authenticated, and the `{product-slug}` must match one of the available plan slugs configured in the application. After successful checkout, the user is redirected back to the application.

### Access Customer Portal

<CodeGroup>
  ```bash Request theme={null}
  GET /api/auth/portal
  ```

  ```text Response theme={null}
  // Redirects to Polar customer portal
  ```
</CodeGroup>

This endpoint redirects authenticated users to their Polar customer portal where they can manage their subscriptions, billing information, and payment methods.

## Next Steps

<CardGroup cols={2}>
  <Card title="Team API" icon="users" href="/api-reference/team">
    Team invitation management
  </Card>

  <Card title="Authentication Feature" icon="lock" href="/features/authentication">
    View the authentication documentation
  </Card>
</CardGroup>