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

# QR codes

QR codes are barcodes. They're a convenient way of distributing data that can be 'read' using a suitable device. 

The QR codes created by aCheck encode a URL and a unique ID parameter. You can include the QR codes on any document or other suitable medium. When the QR code is scanned, a web page is displayed which shows the values stored in aCheck's database relates to the ID parameter.

aCheck uses Model 2 QR codes with Level L Error correction