Understand the QR code standard
A plain-language guide to the grid, quiet zone and error correction behind a readable QR.
A grid that carries data
A QR code encodes data as light and dark square modules. A reader identifies the grid and decodes its pattern. The international specification ISO/IEC 18004 describes QR Code symbology. A standards-based generator still needs appropriate colors, dimensions and testing in its final environment.
Functional patterns help the camera
Three large corner patterns help locate and orient the symbol. Alternating timing modules establish grid spacing. Alignment patterns, present from version 2, help correct distortion. Format and version information help the reader interpret the symbol. These areas should not be treated as decoration.
Four modules of quiet space
The quiet zone is an empty border at least four modules wide on all sides of a regular QR Code. It separates the symbol from nearby graphics. A module is one grid cell, not a fixed number of millimeters. Enlarging the symbol should enlarge its margin too.
Versions describe grid size
Regular QR Code versions range from 1 to 40. Version 1 has 21 × 21 modules; each step adds four modules per side, up to 177 × 177. More content or stronger error correction may require a larger version. At the same print size, a denser grid has smaller cells.
Error correction is a safety net
Levels L, M, Q and H provide different recovery capacity, often described as approximately 7%, 15%, 25% and 30% of codewords. These figures are not a promise that the same proportion of any visible area can be covered. Damage to functional patterns and the distribution of damage matter. QRmaru uses H.
Product limits are not standard limits
QRmaru limits content to 1,600 bytes and applies its own contrast and logo safeguards. These are product choices, not the maximum capacity of the QR standard. UTF-8 characters can use multiple bytes, so character count alone does not determine whether a message fits.
Static codes and real-world checks
A static QR stores its payload directly; it has no built-in service expiry or scan statistics. Encoding a website does not keep that website online. Test the downloaded code and the final print on real devices, with the intended lighting and distance. A decorative illustration is not a test code.