Advanced·12 min read
Complete QR Code Glossary: 50+ Terms Defined
Every QR code term explained in plain language. Bookmark this page as your definitive reference.
Last updated: June 2026
A
- Alignment Pattern
- Small square patterns found in QR codes version 2 and above that help scanners correct for perspective distortion. They appear at predictable positions within the code matrix.
- Alphanumeric Mode
- An encoding mode that supports uppercase letters A-Z, digits 0-9, and nine special characters (space, $, %, *, +, -, ., /, :). Stores up to 4,296 characters.
B
- Binary/Byte Mode
- An encoding mode that supports the full ISO 8859-1 character set (256 characters). Used for URLs, emails, and any data containing lowercase letters or special symbols.
- Bit Stream
- The sequence of binary data encoded within a QR code, including mode indicators, character counts, data, error correction, and padding.
C
- Cell
- See Module. The terms are used interchangeably in QR code documentation.
- Character Count Indicator
- A bit field in the QR data stream that specifies how many characters follow in the current data segment. Its length varies by mode and version.
- Codeword
- A group of 8 bits (one byte) in the QR code data stream. QR codes organize all data and error correction information into codewords.
D
- Dark Module
- A single black square in the QR code matrix. Dark modules represent binary 1 values.
- Data Capacity
- The maximum amount of information a QR code can store. Depends on version (size), error correction level, and encoding mode. Maximum is 7,089 numeric characters at version 40 with EC level L.
- Data Masking
- A process that XORs the data modules with one of eight predefined mask patterns to avoid problematic visual patterns (large dark/light areas) that could confuse scanners.
- DENSO Wave
- The Japanese subsidiary of Toyota that invented the QR code in 1994. Masahiro Hara led the development team. DENSO Wave holds the patent but chose not to exercise it.
- Dynamic QR Code
- A QR code whose destination URL can be changed after creation. Uses a redirect URL that can be updated. Requires a backend service. Contrast with Static QR Code.
E
- ECI (Extended Channel Interpretation)
- A mechanism that allows QR codes to specify which character encoding they use (UTF-8, Shift JIS, etc.), enabling support for international characters.
- Encoding Mode
- The method used to convert data into bits. QR codes support four primary modes: Numeric, Alphanumeric, Byte, and Kanji. Each mode optimizes for different character sets.
- Error Correction
- The ability of QR codes to remain scannable even when partially damaged, using Reed-Solomon error correction codes. Four levels: L (7%), M (15%), Q (25%), H (30%).
- Error Correction Level H
- The highest error correction level, allowing up to 30% of the QR code to be damaged or obscured. Required when adding logos or design elements over the code.
- Error Correction Level L
- The lowest error correction level (7% recovery). Produces the smallest QR codes and maximizes data capacity, but offers minimal damage tolerance.
- Error Correction Level M
- Medium error correction (15% recovery). The default for most QR code generators. A good balance between capacity and resilience.
- Error Correction Level Q
- Quartile error correction (25% recovery). Recommended for QR codes that will be printed on materials subject to wear.
F
- Finder Pattern
- The three large squares in the corners of every QR code (top-left, top-right, bottom-left). They allow scanners to detect the QR code's position and orientation.
- Format Information
- A 15-bit string stored near the finder patterns that encodes the error correction level and the data mask pattern used.
G
- Galois Field
- The mathematical field (GF(2^8) = GF(256)) used in Reed-Solomon error correction calculations. Each element corresponds to a possible codeword value.
I
- ISO/IEC 18004
- The international standard that defines QR code symbology. The current version is ISO/IEC 18004:2015. All QR code specifications derive from this standard.
K
- Kanji Mode
- An encoding mode specific to Japanese Shift JIS characters. Encodes each character in 13 bits, supporting up to 1,817 characters.
L
- Light Module
- A single white square in the QR code matrix. Light modules represent binary 0 values.
- Logo Overlay
- A design technique where a brand logo is placed over the center of a QR code. Requires error correction level H (or at minimum Q) to ensure scannability.
M
- Mask Pattern
- One of eight predefined patterns used during data masking. The generator evaluates all eight and selects the one that produces the best visual balance.
- Micro QR Code
- A smaller variant of the QR code with only one finder pattern (instead of three). Supports versions M1 through M4 and is used for small items like electronic components.
- Mode Indicator
- A 4-bit field at the beginning of each data segment that identifies the encoding mode (0001=Numeric, 0010=Alphanumeric, 0100=Byte, 1000=Kanji).
- Module
- The smallest unit of a QR code — a single square that is either dark (black) or light (white). The entire QR code is a grid of modules.
N
- Numeric Mode
- An encoding mode optimized for digits 0-9. The most efficient mode, storing three digits in 10 bits. Supports up to 7,089 characters.
P
- Padding Codewords
- Alternating bytes (0xEC and 0x11) added after the data to fill the remaining capacity of the QR code version selected.
Q
- QR Code
- Quick Response Code. A two-dimensional matrix barcode invented in 1994 by DENSO Wave. Can store URLs, text, contact information, WiFi credentials, and more.
- QRishing
- A phishing attack conducted via QR codes. Attackers replace legitimate QR codes with malicious ones that redirect users to fake websites.
- Quiet Zone
- The margin of blank (white) space that must surround the QR code on all sides. The standard requires a minimum of 4 modules of quiet zone.
R
- Reed-Solomon Error Correction
- The mathematical algorithm used by QR codes to generate error correction codewords. Allows recovery of data even when parts of the code are damaged.
- Remainder Bits
- Zero-padding bits added after the final codeword to fill the QR code's bit capacity exactly. The number required varies by version (0, 3, 4, or 7 bits).
S
- Separator
- A one-module-wide white border around each finder pattern that ensures the finder pattern is clearly distinguishable from the data area.
- Static QR Code
- A QR code whose encoded data is fixed at creation time and cannot be changed. The data is stored directly in the code itself. Contrast with Dynamic QR Code.
- Structured Append
- A feature allowing a single dataset to be split across up to 16 linked QR codes. Each code contains a header indicating its position in the sequence.
T
- Timing Pattern
- Alternating dark and light modules in a single row and column connecting the finder patterns. They help scanners determine module coordinates.
V
- vCard
- A standard file format (.vcf) for electronic business cards. QR codes can encode vCard data to allow one-scan contact saving on smartphones.
- Version
- The size designation of a QR code, ranging from 1 (21×21 modules) to 40 (177×177 modules). Each version increment adds 4 modules per side.
- Version Information
- An 18-bit field found in QR codes version 7 and above, placed near the finder patterns. It encodes the version number for the scanner.