One- and two-dimensional barcodes, including Quick Response (QR) codes, have become a convenient way to communicate small amounts of information from physical objects to mobile devices. While there is much discussion, awareness, and proposed use of such barcodes, both in academia and in industry, to our knowledge there has not been a systematic and in-depth analysis of the actual ecosystem surrounding these codes. To fill this gap, we analyze a log of all scans performed by users of a popular QR and barcode scanning app available for Android, iPhone, and Windows Phone. Our dataset includes over 87 million scans performed over a 10-month period from May 2013 to March 2014. We examine general use patterns of QR and barcodes in the wild and identify common and uncommon uses and misuses. We see the presence of both conventional (e.g., web) and emerging (e.g., Bitcoin) uses of QR codes, and develop an informed understanding of the types of QR codes being created and how users interact wit...