Purpose: This paper aims to explain the nature of quick response (QR) codes and their possible applications in libraries. Design/methodology/approach: Existing uses, applications, and functionality of QR codes are looked at, before turning to the limited existing use of QR codes in libraries. The author then suggests many different ways QR codes could be used in our libraries. Findings: Most of our users are likely to be able to use QR codes if they install a free reader onto their camera phones or other mobile devices. An already high and further increasing number of people own suitable devices. There are many ways QR codes can be used, with the most exciting applications relying on the use of the internet from mobile devices. The main restrictions on their take up is likely to be increasing awareness of QR codes and carefully marketing services based on QR codes to our users. Originality/value: Outside Japan few libraries have implemented services based on QR codes. This article is the first of its kind aimed at libraries and it shows how we can use them to take advantage of the mobile devices in many of our users" pockets.