EAN-13Retail shelf products worldwide. 12 digits plus a check digit the tool appends. Scanners expect the guard bars to run longer than the data.
UPC-AThe US flavour of EAN. 11 digits plus a check digit; encoded as an EAN-13 with a leading zero.
Code 128Logistics and internal labels. Any printable ASCII, with Code C packing digit pairs so numeric payloads come out half as wide.
ITF-14Shipping cartons. 13 digits plus a check digit, printed with bearer bars so a partial scan cannot read as a shorter valid code.
ModuleThe width of the narrowest bar. Retail scanners are speced for 0.33 mm at 100% magnification; going under 0.26 mm risks misreads.