QR codes are two-dimensional barcodes that can store large amounts of data and link to websites and other online content. They were developed in 1994 for use in manufacturing but are now commonly used to provide additional information through smartphones. Libraries employ QR codes to link patrons to audio files, catalog records, tutorials and more from exhibits, materials and online presences. While awareness of QR codes is growing, some weaknesses remain as not all patrons have smartphones or know how to use them.