Android users who want to download a QR Code scanner from Google Play can just go to this page.
https://play.google.com/store/search?q=qr+code&c=apps
Given the rapid increase in QR Code usage, it seems very likely that a native QR Code scanner will be part of Android very soon and if that does turn out to be the case you shouldn’t need to download a separate QR Code reader application.
Note that different QR Code scanner apps offer different functionality and some don’t work as well as others.
(Written in January 2018)