Barcode (Overview)

A barcode is any visual, machine-readable representation of data. The earliest barcodes were 1D (linear) — patterns of vertical bars and spaces of varying widths. Newer 2D barcodes like QR codes and Data Matrix store much more information in a square pattern of dark and light modules.

Receipts typically include 2-3 barcodes: a Code 128 transaction barcode at the bottom (for returns and customer service), individual UPC or EAN-13 barcodes printed near each line item (less common today), and increasingly a QR code for surveys, digital coupons, or order tracking.

Barcode scanning at the point of sale is one of the most consequential inventions of 20th-century retail — it eliminated keying errors, enabled real-time inventory management, and made checkout 5-10× faster.

For receipt design, the choice of barcode format matters: 80mm thermal width comfortably fits Code 128 and QR codes; UPC-A barcodes need around 35mm; gas-pump receipts at 57mm rarely include barcodes at all (the transaction is identified by the auth code).