> **Description:** Illustrated guides showing payment flows for online, in-store, and QR code transactions.

# How it works

The following guides illustrate how the ePayment PSP API works in different scenarios:

* [How it works with online payments](https://developer.vippsmobilepay.com/docs/APIs/psp-epayment-api/how-it-works/online-psp.md)
* [How Express works](https://developer.vippsmobilepay.com/docs/APIs/psp-epayment-api/how-it-works/express-psp.md)

> **Full site overview:** For every page in this documentation, read [https://developer.vippsmobilepay.com/llms.txt](https://developer.vippsmobilepay.com/llms.txt).