The Auto mode allows the barcode software to auto detect the data, determine the most optimized variation and, if required, switch between the variations automatically. With the switching, the specifications also cater to an Auto mode to help users create the barcode easily. Each of the variations is targeted for specific purposes and switching between the different variations is possible with additional control characters.

Under the industry specifications, this barcode supports three different variations : Code 128 A, Code 128 B and Code 128 C. The reason is that this barcode can support the full ASCII character set, is flexible and can support very dense (number of characters per inch) barcode. Code128 barcode is currently one of the most widely used barcode.