QR Code Glossary
40 technical terms explained in depth — from finder patterns and Reed-Solomon error correction to UPI intents, GS1 Digital Link, and print sizing. Written and reviewed by QR systems engineers.
Encoding & Structure
How data becomes modules: patterns, versions, masks, and encoding modes.
Module
The smallest single square unit of a QR code matrix, representing one binary bit — dark for 1, light for 0.
Finder Pattern
Three identical concentric square markers at the top-left, top-right, and bottom-left corners of every QR code, enabling 360-degree orientation detection.
Timing Pattern
A single-module-wide alternating dark-and-light track running horizontally and vertically between the finder patterns, giving the scanner a ruler for measuring module pitch and symbol density.
Alignment Pattern
A 5×5 concentric-square marker placed in a grid across larger QR symbols (Version 2 and up) that corrects local warping, letting scanners read codes printed on curved, tilted, or uneven surfaces.
QR Code Version
The size class of a QR code symbol, numbered 1 to 40, where each step adds 4 modules per side — Version 1 is 21×21 modules and Version 40 is 177×177.
Mask Pattern
One of 8 XOR patterns applied to the data modules of a QR code to break up large dark or light areas that would confuse the scanner, recorded in the format information bits.
Encoding Modes
The four data compaction schemes in QR codes — numeric, alphanumeric, byte, and kanji — each with a 4-bit mode indicator and a packing method tuned to its character set.
Structured Append
A QR feature that splits one logical payload across up to 16 separate symbols, each carrying its position, the total count, and a parity byte so the scanner can reassemble them in order.
Eye Pattern (Custom Finder Style)
A styled rendering of the QR finder patterns — the “eyes” of the code — where the outer square and inner dot take custom shapes and colors while preserving the 1:1:3:1:1 detection ratio.
Error Correction
Reed-Solomon math and the L/M/Q/H resilience levels.
Reed-Solomon Error Correction
A non-binary BCH polynomial error correction algorithm used in QR codes to mathematically reconstruct damaged or missing data codewords.
Error Correction Level
One of four Reed-Solomon redundancy levels (L, M, Q, H) that determines how much of a QR code can be damaged while remaining decodable.
Printing & Design
Sizes, contrast, styling, and print production guidance.
Quiet Zone
The mandatory unprinted white border of at least 4 modules surrounding all four sides of a QR code, required for reliable scanner binarization.
SVG vs PNG for QR Codes
The two export formats that matter for QR codes: SVG (vector, infinitely scalable, ideal for print) versus PNG (raster, fixed pixels, ideal for screens) — choose by destination.
Dot Style (Rounded Modules)
A decorative rendering that draws QR data modules as rounded dots or circles instead of squares — attractive for branding, but it must preserve module separation and contrast to stay scannable.
Logo Safe Area
The central region of a QR code where a brand logo may be overlaid — kept clear of finder, timing, and alignment patterns, sized so error correction can reconstruct the covered modules.
Contrast Ratio
The luminance difference between a QR code’s dark modules and its light background — the single most important optical property for reliable scanning, requiring dark-on-light with strong separation.
QR Code Print Size
The physical dimensions of a printed QR code, driven by module width: plan at least 2×2 cm for close scanning, scale by the 10:1 distance rule, and never print modules below ~0.5 mm.
Security
URL reputation, homograph attacks, and safe scanning.
Google Safe Browsing
Google’s threat-intelligence service that flags malicious URLs — the backend that lets QR scanners, browsers, and apps warn users before opening a phishing or malware link from a code.
Punycode (IDN Encoding)
The ASCII-compatible encoding (RFC 3492) that represents non-Latin domain names — the xn-- labels behind internationalized domains — critical for spotting homograph phishing in QR URLs.
Standards
ISO specifications, GS1 modes, and character encodings.
vCard Format
An IETF-standardized electronic business card format (RFC 2426 for v3.0, RFC 6350 for v4.0) encoded into QR codes for instant contact import on iOS and Android.
MeCard Format
A compact contact-exchange format created by NTT DoCoMo (MECARD:N:name;TEL:...;;) that encodes business-card data in fewer characters than vCard, popular for simple contact QR codes.
GS1 Digital Link
The GS1 standard that encodes product identifiers (like the GTIN) as an ordinary web URI — e.g. https://id.gs1.org/01/09520123456788 — so one QR code serves shoppers, scanners, and supply-chain systems.
QR Code Model 1 vs Model 2
The two generations of the QR symbology: the original Model 1 (versions 1–14, never ISO-standardized) and Model 2 (versions 1–40 with alignment patterns), which is the QR code everyone uses today.
FNC1 (Function 1 Character)
A special mode indicator that turns a QR code into a GS1-compliant symbol: in first position it signals GS1 Application Identifier data, in second position it marks an industry-specific application.
ECI Mode (Extended Channel Interpretation)
A QR mode indicator (0111) followed by a designator number that tells the scanner which character encoding the bytes use — most commonly 000026 for UTF-8.
Scanning & Analytics
Scan distance, analytics, deep links, and campaign tracking.
Scan Analytics
The measurement of QR code scans over time — counts, devices, locations, and referrers — collected when scans pass through a dynamic QR redirect service.
Scan Distance
The range of distances from which a QR code can be reliably decoded — governed by a rule of thumb that maximum distance is roughly ten times the symbol’s width.
UTM Parameters
The five standard URL query tags (utm_source, utm_medium, utm_campaign, utm_term, utm_content) that attribute QR-driven web traffic to the exact code, placement, and campaign in analytics.
Payments
Bitcoin, Ethereum, EPC GiroCode, UPI, and EMVCo payment QR formats.
EMVCo TLV (Tag-Length-Value)
The international data encoding standard used by EMVCo for payment QR codes (Pix, UPI, SGQR, Raast, PromptPay), using nested Tag-Length-Value data objects.
BIP-21 (Bitcoin URI Scheme)
The standardized bitcoin: URI format (bitcoin:address?amount=0.5&label=...) that lets QR codes open a wallet with the recipient address and payment amount pre-filled.
EIP-681 (Ethereum URI Scheme)
The standardized ethereum: URI format for payment requests (ethereum:0xaddress?value=... or ethereum:pay-.../transfer) that lets QR codes open a wallet with address, amount, and token details pre-filled.
EPC GiroCode (European Payment QR)
The European Payments Council QR format for SEPA credit transfers — a line-based BCD payload with beneficiary, IBAN, and amount that banking apps scan to pre-fill a bank transfer.
UPI Intent (India Payment QR)
The upi://pay deep-link format that lets a QR code open any UPI app (GPay, PhonePe, Paytm, BHIM) with the payee VPA, name, amount, and note pre-filled for instant settlement.
Formats & Variants
Static vs dynamic codes, Micro QR, rMQR, and contact formats.
Data Matrix
A 2D square or rectangular matrix barcode standardized under ISO/IEC 16022, widely used in pharmaceutical, aerospace, and electronics manufacturing for ultra-small part marking.
Static QR Code
A QR code whose encoded data is final and immutable — the destination URL, text, or contact details are baked into the pattern itself and can never be changed or tracked.
Dynamic QR Code
A QR code that encodes a short redirect URL instead of the final data, so the destination can be changed after printing and every scan can be counted and analyzed.
Short Link
A compact redirect URL (often on a branded domain) that sits behind a dynamic QR code, keeping the encoded payload tiny so the printed symbol stays small, sparse, and easy to scan.
Deep Link
A URL that opens a specific screen inside a mobile app rather than a web page, letting a QR code launch app content directly — with a web fallback for users without the app.
Micro QR Code
A compact QR variant with a single finder pattern and symbol sizes from 11×11 to 17×17 modules, designed for marking very small parts and labels where a full QR code cannot fit.
rMQR Code
A rectangular variant of the QR code — taller widths than heights from 43×7 up to 139×17 modules — designed for narrow spaces like receipts, labels, and component reels where a square code cannot fit.