# API Payment Switch

SumUp API Payment Switch is a light integration where your app opens the SumUp app to request and execute a payment. This integration approach has been the go-to solution for web аpplications before the platform-agnostic [Cloud API](/terminal-payments/cloud-api) was released.

Your app initiates a request to charge a card, opens the SumUp app on the merchant's mobile device, and we handle the rest. Once the payment has been processed, the transaction result is communicated back, and the merchant is returned to your app.

The API integration also allows the possibility to pre-fill the checkout amount and cardholder information, and send a receipt via SMS or email. You can use the cash option, not available in our SDK, for better reporting and management of your funds in the SumUp dashboard.

Activate the [mandatory authorization scopes](/tools/authorization/oauth/#authorization-scopes) for a smooth performance. They require an access token for your client application for authentication and authorization with the SumUp REST API.

## Integration Documentation

You can find additional documentation for the different mobile platforms below:

- Integrate the [iOS API](https://github.com/sumup/sumup-ios-url-scheme)
- Integrate the [Android API](https://github.com/sumup/sumup-android-api)