A barcode is a visual, machine-readable representation of data consisting of parallel lines, geometric patterns, or dots printed on a label or directly on a product. The width and spacing of these elements encode information—such as a product identifier, price, or serial number—that a barcode scanner decodes in milliseconds by measuring reflected light. First patented in 1952 and commercialized in the 1970s with the introduction of the UPC standard, barcodes now underpin global supply chains, retail point-of-sale systems, healthcare, and logistics.

Barcodes exist in two primary families: one-dimensional (1D) barcodes, which encode data horizontally in a series of lines and spaces (e.g., Code 128, UPC-A, EAN-13), and two-dimensional (2D) barcodes, which encode data both horizontally and vertically using patterns of squares or dots (e.g., QR Code, Data Matrix, PDF417). A 1D barcode on a grocery item like a can of soup typically stores a 12-digit UPC, while a 2D Data Matrix on a circuit board can store hundreds of characters including serial numbers and manufacturing dates.

Choosing the right barcode type depends on data density requirements, scan distance, substrate material, and industry standards. For example, a Zebra ZD421 thermal label printer can produce both 1D and 2D barcodes at resolutions up to 300 dpi, while a Honeywell DS2208 handheld scanner reads virtually all common symbologies in a single pass. Understanding the barcode ecosystem—from symbology selection to label media to reader hardware—is essential for building a reliable AIDC (Automatic Identification and Data Capture) system.