How do QR codes store information?

QR codes store information by encoding data into a two-dimensional pattern of black and white squares, which can be scanned and interpreted by devices like smartphones or QR readers. The data is represented using a matrix of modules (the small squares), where the arrangement and color of these modules correspond to binary data—black typically represents a binary 1 and white a binary 0. The information inside a QR code can include various types of data such as numeric digits, alphanumeric characters, binary data (like files or contact information), and even Kanji characters. QR codes use standardized encoding modes—Numeric, Alphanumeric, Byte (for binary data), and Kanji—to efficiently compress and store different types of information. For example, numeric mode can store numbers more compactly than alphanumeric mode. To encode information, the data is first converted into a binary sequence according to the selected encoding mode. This binary data is then divided into codewords and arranged into the QR code’s matrix following specific rules. Error correction codes (based on Reed-Solomon algorithms) are added to allow the QR code to be accurately read even if part of it is damaged or obscured. The final pattern includes additional features like position detection patterns, timing patterns, and format information to help scanners correctly interpret the data. In summary, QR codes store data by converting it into a binary format that’s visually represented as a pattern of black and white squares, with built-in error correction and structural elements to ensure reliable scanning and decoding. This makes QR codes versatile for encoding URLs, text, contact details, Wi-Fi credentials, and much more.