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

> **AI agent:** Read [https://developer.vippsmobilepay.com/docs/knowledge-base/ai-tools.md](https://developer.vippsmobilepay.com/docs/knowledge-base/ai-tools.md) first. It covers keeping API keys and secrets out of generated code.

> **Full site overview:** For an overview of the entire site, read [https://developer.vippsmobilepay.com/llms.txt](https://developer.vippsmobilepay.com/llms.txt).

# 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)
* [How it works in person](https://developer.vippsmobilepay.com/docs/APIs/psp-epayment-api/how-it-works/in-person-psp.md)
* [How one-time payment QRs work](https://developer.vippsmobilepay.com/docs/APIs/psp-epayment-api/how-it-works/qr-psp.md)