QR Code Glossary

QR code: A two-dimensional matrix barcode that stores data in a grid of dark and light modules, readable by a phone camera. QR stands for Quick Response. It is defined by the open ISO/IEC 18004 standard.
Static QR code: A QR code that encodes its destination directly into the pattern. It cannot be changed after creation, never expires, and requires no account or server — making it permanent and tamper-evident.
Dynamic QR code: A QR code that encodes a short redirect URL the owner controls. The destination can be changed after the code is printed, and each scan can be counted, without altering the printed image.
Module: A single dark or light square in the QR code grid. The number of modules per side grows with the QR version, from 21×21 (version 1) up to 177×177 (version 40).
Finder pattern: The three large concentric squares in the corners of a QR code. They let a scanner detect the code's position, size, and orientation from any angle, which is why a QR code scans even when rotated.
Alignment pattern: Smaller square patterns that help scanners correct for distortion on larger QR versions, improving reliability when the code is on a curved or angled surface.
Quiet zone: The blank margin around a QR code, at least four modules wide. Without it, scanners cannot tell where the code ends, so cropping a code tight to a design breaks scanning.
Error correction: Built-in redundancy that lets a QR code be read even when partly damaged or obscured. It uses Reed–Solomon coding and comes in four levels: L, M, Q, and H.
Error-correction level L / M / Q / H: The four redundancy levels of a QR code: L recovers roughly 7% of the code, M about 15%, Q about 25%, and H about 30%. Higher levels survive more damage and allow a centered logo, at the cost of a denser code.
QR version: The size class of a QR code, from version 1 (21×21 modules) to version 40 (177×177). The generator picks the smallest version that fits the data at the chosen error-correction level.
Data capacity: The maximum content a QR code can hold. At version 40 the limits are 7,089 numeric characters, 4,296 alphanumeric characters, or 2,953 bytes.
Micro QR code: A compact QR variant for very small spaces. It holds less data and uses a single finder pattern, useful on tiny parts and labels, though scanner support is less universal than standard QR.
vCard QR code: A QR code encoding a full digital contact card — name, phone, email, company — so scanning saves the contact to a phone in one tap. The digital replacement for a paper business card.
WiFi QR code: A QR code encoding a network name, password, and security type, so scanning prompts a phone to join the WiFi automatically without typing the password. It works fully offline.
Masking: A process that flips module patterns to avoid large blank areas or repeated shapes that could confuse scanners. The generator chooses the optimal mask automatically; it changes the look but not the content.
Scan: The act of a camera reading a QR code, decoding the module pattern, and triggering the encoded action — opening a link, joining WiFi, or saving a contact.
Redirect (short link): The intermediate URL a dynamic QR code points to. The owner can repoint it to any destination, which is what makes a dynamic code editable and trackable.
Scan analytics: Aggregate, anonymous data about dynamic QR scans — total count, approximate location, device type, and time — used to measure campaigns. It does not identify the individual scanner.
Quishing: QR-code phishing: placing a malicious QR code, often a sticker over a legitimate one, to send victims to fake login or payment pages. Defenses include checking for tampering and previewing the URL before opening.
Quiet response: The origin of the name QR: codes were designed for quick (rapid) decoding compared to traditional one-dimensional barcodes, hence Quick Response.
NFC tag: A wireless chip read by tapping a phone against it, an alternative to a scanned QR code. NFC needs a physical chip and no line of sight; a QR code is free to print on anything but needs a camera view.
Deep link / universal link: A URL that opens a specific screen inside a mobile app rather than a browser. A QR code pointing at a universal link launches the app directly if it is installed.
CMYK vs RGB: Color models for print (CMYK) and screens (RGB). Designing a QR code in RGB and printing in CMYK can shift colors and reduce contrast, so codes should be proofed in CMYK for reliable print scanning.
Vector format (SVG / EPS / PDF): Resolution-independent file formats that keep a QR code razor-sharp at any print size, unlike raster PNG which can blur when scaled up. Vector is preferred for professional printing.
Smart redirect: A dynamic QR behavior that detects the scanning device and routes accordingly — for example sending iPhone users to the App Store and Android users to Google Play from a single printed code.

Ready to make one?