> For the complete documentation index, see [llms.txt](https://oneupi.gitbook.io/integration/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://oneupi.gitbook.io/integration/introduction.md).

# Introduction

* One UPI library acts as a mediator between your app and UPI apps (*which are already installed in user devices*).
* Our library is based on [***these***](https://www.npci.org.in/sites/default/files/UPI%20Linking%20Specs_ver%201.6.pdf) specifications provided by *NPCI (National Payments Corporation of India)*.
* This library is based on Android Intent based operations and Blockchain validation.
* Whenever payment is initiated, it simply sends the `Intent` to the UPI apps installed on device.
* When transaction is done, response is returned from library.
* Payment will be only processed when payee is having a **valid merchant account of UPI**. Otherwise, payment won’t be successful. We have designed the code such to reduce the clutter of payment notes in your ledger book. Note: This *won’t work for general UPI payee user*.

![](/files/QrIeE5ttsz3Fxn9KL8Em)