The symbology of barcode is an identification technology that encodes information into parallel bars and spaces of varying thickness. The term "symbology" is used to describe the standards that specify how data is encoded in the bars and spaces. There are many barcode symbologies in use today. The UPC/EAN barcode is common in the retail industry.

The Code 39 barcode (also known as 3 of 9) is widely used in wholesale and distribution.

The 93 and 128 barcodes were developed in an attempt to reduce the amount of space required for the barcode. Other barcode symbologies are used for different applications, and new symbologies are being developed as scanning technology advances.