QR code glossary: terms and definitions

Jump to a term

• QR code
• Static QR code
• Dynamic QR code
• Payload
• Encoding mode
• Module
• QR version
• Finder pattern
• Alignment pattern
• Timing pattern
• Mask pattern
• Quiet zone
• Contrast ratio
• Error correction level (L, M, Q, H)
• Reed-Solomon codes
• Data capacity
• SVG and PNG
• QR code with a logo
• Short URL or redirect URL
• Scan analytics
• UTM parameter
• Smart redirect
• Retargeting pixel
• Campaign QR code
• vCard QR code
• GS1 Digital Link
• Micro QR code
• ISO/IEC 18004
• Quishing (QR phishing)

QR code

A QR code is a two-dimensional matrix barcode that stores data in a grid of light and dark modules. A compatible reader locates the finder patterns, interprets the grid, applies error correction, and returns the encoded payload.

The payload can be a web address, text, contact data, WiFi credentials, or another supported format. A QR code can store that payload directly or carry a short link that QRLynx resolves dynamically.

See the current ISO/IEC 18004 QR Code specification.

Static QR code

A static QR code stores its final payload directly in the symbol. A URL code opens that exact URL, while a WiFi, text, email, or contact code exposes the encoded data to the scanner without a redirect lookup.

The printed payload cannot be changed. A static URL code can remain usable for as long as its destination remains available, and it does not depend on a QR platform for resolution. Choose static when the data is final. Choose dynamic when the destination may change or QRLynx scan analytics are part of the campaign.

Dynamic QR code

A dynamic QR code stores a short redirect URL instead of the final destination. QRLynx looks up the saved destination when someone scans, so the owner can update that destination while keeping the same printed pattern.

The redirect request also makes QRLynx scan analytics and plan-based campaign controls possible. A dynamic code uses one active dynamic slot and depends on its assigned short link remaining active.

See also: Static QR code and the dynamic URL QR code generator.

Payload

The payload is the data stored in the QR symbol. It may be an HTTPS URL, plain text, WiFi credentials, a vCard, a calendar event, an email address, a phone number, or a payment URI.

The payload format tells a compatible scanner what action to offer. A URL can open a browser, a mailto: payload can open an email composer, and a WiFi payload can present a join-network action. The exact action and supported fields vary by device and scanner.

Encoding mode

An encoding mode tells a QR reader how the following data is represented. Standard QR Code supports numeric, alphanumeric, byte, and Kanji modes, with additional control modes defined by the specification.

An encoder can divide a payload into segments and select efficient modes automatically. Numeric data generally needs fewer modules than the same number of arbitrary byte characters, so character set and segment choice can affect symbol density.

Module

A module is one light or dark cell in a QR code grid. QR dimensions are described in modules because the same symbol can be rendered at many pixel or print sizes.

Version 1 is 21 by 21 modules. Each later version adds four modules per side, ending with Version 40 at 177 by 177. The physical module size, total symbol size, material, lighting, and viewing distance all affect real-world readability.

Use the QR code print size guide to choose a starting size, then test the final artwork in its intended setting.

QR version

A QR version is the grid size of a standard QR Code. The specification defines Versions 1 to 40, from 21 by 21 modules to 177 by 177 modules. Each step adds four modules to the width and height.

An encoder chooses a version that can hold the payload at the selected error correction level. More data or stronger correction can require a higher version, which produces a denser symbol. DENSO WAVE publishes the version and capacity tables.

Shortening the encoded URL can reduce density. A dynamic QR code does this by storing a short redirect URL.

Finder pattern

The finder patterns, also called position detection patterns, are the large square targets in the top-left, top-right, and bottom-left corners of a standard QR Code. Their 1:1:3:1:1 black-and-white ratio helps a reader locate the symbol and determine its orientation.

Keep all three patterns clear. A logo, crop, sticker edge, or decorative element that covers one can prevent a scanner from locating the grid even when the data area is otherwise intact.

Alignment pattern

Alignment patterns are the smaller square targets placed at defined positions in Version 2 and larger QR Codes. They give the decoder extra reference points for correcting geometric distortion after it locates the three main finder patterns.

Version 1 has no alignment pattern. Larger versions add more at positions defined by the specification. Keep these patterns unobstructed when adding artwork or testing a customized code.

Timing pattern

The timing patterns are alternating dark and light modules running horizontally and vertically between the finder-pattern areas. They help the decoder establish the module grid and determine the symbol's dimensions.

A decorative frame can sit outside the quiet zone, but artwork should not cover the timing lines or the finder patterns. Test customized symbols at their actual print size.

Mask pattern

A mask pattern changes the light and dark arrangement of data modules without changing the decoded payload. QR Code defines eight masks. The encoder evaluates each one against penalty rules and stores the selected mask number in the symbol's format information.

The penalty rules discourage long same-color runs, large same-color blocks, finder-like sequences in the data area, and an unbalanced dark-to-light ratio. With the same payload and encoder settings, mask selection is normally deterministic. Changing the payload, version, or error correction can produce a different symbol.

Quiet zone

The quiet zone is the clear margin around a QR code. A standard QR Code needs an empty margin at least four modules wide on every side so a reader can separate the symbol from nearby text, borders, or artwork.

Keep the quiet zone clear in the final printed layout, not only in the downloaded file. Cropping, a close border, or artwork placed inside the margin can make detection less reliable. DENSO WAVE shows the four-module requirement in its code area guide.

Learn more in the QR code design guide.

Contrast ratio

Contrast ratio describes the visual difference between the dark and light areas of a QR code. Strong contrast helps a camera separate modules from the background in the intended lighting and material.

Dark modules on a light, plain background are the most predictable starting point. Color designs can also scan when the module and background values remain clearly separated. Test the exported code on the final screen or printed material because glare, texture, ink, and display brightness can change the effective contrast.

Use the QR code readability checker before the final physical test.

Error correction level (L, M, Q, H)

Error correction level controls how much redundant data a QR symbol carries. The four levels can restore approximately 7% of codewords at L, 15% at M, 25% at Q, and 30% at H. These percentages describe codewords, not a guaranteed percentage of visible surface damage.

Higher correction can help with dirt, scratches, or a centered logo, but it also increases symbol density for the same payload. The right level depends on the print environment, code size, payload, and design. DENSO WAVE explains the tradeoff in its error correction guide.

See also: Reed-Solomon codes and QR code with a logo.

Reed-Solomon codes

Reed-Solomon coding is the error-correction method used in QR Codes. The encoder adds recovery codewords to the data, and the decoder can use that redundancy when some codewords are unreadable or incorrect.

The selected error correction level controls how much recovery data is added. DENSO WAVE's technical explanation notes that the percentages are measured against total codewords, which is why visible damage area is only a rough guide.

Data capacity

Data capacity is the amount of information a QR Code can store. It depends on the symbol version, error correction level, and encoding mode. QR encoding does not compress an arbitrary payload.

At Version 40 and level L, the published maximums are 7,089 numeric characters, 4,296 alphanumeric characters, or 2,953 bytes. Stronger error correction reduces the available data capacity. DENSO WAVE lists the values in its QR Code outline specification.

A shorter payload usually creates a less dense symbol. For web destinations, a dynamic QR code stores a short redirect URL instead of the full destination.

SVG and PNG

SVG is a vector format that describes the QR artwork as shapes, so it can be enlarged without turning the module edges into visible pixels. PNG is a raster image made from a fixed pixel grid.

Use SVG when a printer or designer needs scalable artwork. Use PNG when the target size is known and the exported pixel dimensions are sufficient. QRLynx registered accounts include raster downloads, while SVG starts on the paid Starter+ plan.

See the high-resolution QR code guide for format and print checks.

QR code with a logo

A QR code with a logo is a standard QR symbol with an image placed over part of its data area. Error correction can recover some obscured data, but readability still depends on logo size, placement, payload density, correction level, contrast, and print quality.

QRLynx lets the creator choose L, M, Q, or H. Keep the logo centered and restrained, preserve the finder and timing patterns and quiet zone, then test the downloaded code on current phones at the final physical size before a large print run.

Follow the QR code logo guide for the full workflow.

Short URL or redirect URL

A short URL, also called a redirect URL, is the compact address stored in a dynamic QR code. QRLynx assigns the code a short link on its redirect-domain pool, receives the scan request, and forwards it to the saved destination.

This layer supports editable destinations, scan analytics, and eligible rule-based routing while keeping the encoded short link unchanged. The link remains assigned to that saved dynamic code while the code and account state allow it to resolve.

Scan analytics

Scan analytics are measurements recorded when a dynamic QR code resolves through QRLynx. The dashboard provides totals and time trends, with additional location, device, operating-system, and browser detail available by plan.

QRLynx shows code owners aggregated results rather than scanner identities or IP addresses. A scanner becomes identifiable to the owner only when the person voluntarily submits information through a separate form or destination experience.

Analytics history is available for 3 months on Starter, 1 year on Starter+, 2 years on Pro, 3 years on Business, and all available analytics history on Enterprise. Across the full plan window, QRLynx keeps totals, charts, top QR codes, and the location, device, operating-system, and browser breakdowns available to the plan. Business and Enterprise can also export analytics for the selected period.

Static QR codes do not resolve through QRLynx, although the destination website can record its own ordinary web analytics.

See the QRLynx analytics guide.

UTM parameter

UTM parameters are campaign labels added to a destination URL as query parameters. Analytics tools can read them to group visits by source, medium, campaign, content, or term.

For print, a URL might use utm_source=store_poster, utm_medium=qr, and utm_campaign=summer_menu. Create a separate content value for each placement when you need to compare posters, packages, tables, or mail pieces.

The free QRLynx UTM Builder assembles and encodes the destination URL before you create the QR code.

Smart redirect

A smart redirect selects a destination from saved rules when a dynamic QR code is scanned. QRLynx rules can match the scanner's device operating system, country, or a configured time window. A fallback destination handles scans that do not match a rule.

One printed code can therefore open an iOS or Android destination, a country-specific page, or a time-sensitive page without changing its pattern. Smart redirect rules are available on Pro and higher plans.

See smart redirect rules for QR codes.

Retargeting pixel

A retargeting pixel is an advertising or analytics tag connected to a visitor event. When an eligible QRLynx dynamic code has a tag configured, the scanner passes through a short intermediary page that can load the tag before continuing to the destination.

QRLynx Enterprise supports Meta Pixel, Google Tag Manager, and Google Analytics 4 identifiers for this flow. Owners are responsible for the consent notices, privacy disclosures, and platform settings required for their audience and jurisdiction.

See retargeting pixels for QR codes.

Campaign QR code

A campaign QR code is a QR code assigned to a specific marketing placement or audience. The symbol is ordinary QR technology. The campaign value comes from a clear destination, a placement-specific name, optional UTM parameters, and measurable results.

Create separate dynamic codes for placements you want to compare, such as a package, store poster, event handout, and direct-mail piece. QRLynx shows scan activity for each code, while destination analytics can connect those visits to signups or purchases.

vCard QR code

A vCard QR code stores contact data in a vCard payload. Compatible phones can read fields such as name, phone, email, company, job title, address, and website, then offer a save-contact action. The vCard format is defined in RFC 6350.

A detailed vCard can create a dense static symbol because every field is encoded in the grid. For a business-card-sized print, QRLynx's Digital Business Card QR code opens a hosted card with a save-contact button and keeps the printed redirect editable.

GS1 Digital Link

GS1 Digital Link is a GS1 standard for expressing identifiers, such as a GTIN, inside an HTTPS URI. A QR code can carry that URI so a phone can open it as a web address and a GS1-aware system can parse supported identifiers and attributes.

In a GS1 Digital Link path, Application Identifier 01 introduces a 14-digit GTIN. Qualifiers can identify a batch, serial item, or other supported product context more precisely.

QRLynx can generate a GS1 Digital Link URI in static mode or use a dynamic QRLynx short link that resolves to the configured destination. Dynamic mode uses an active dynamic slot and supports QRLynx analytics. QRLynx's scope here is GS1 Digital Link URI generation and resolution. Print approval, resolver certification, and retailer acceptance are separate processes.

Read the GS1 Digital Link explainer, or create a GS1 Digital Link QR code.

Micro QR code

Micro QR Code is a compact QR-family symbol with one position detection pattern. Its four versions, M1 to M4, range from 11 by 11 to 17 by 17 modules and need a two-module quiet zone.

Capacity is small. DENSO WAVE lists a maximum of 35 numeric or 21 alphanumeric characters for M4 at level L, with lower capacity at stronger correction levels. Reader support should be confirmed for the equipment and workflow before printing.

See DENSO WAVE's Micro QR Code specification summary.

ISO/IEC 18004

ISO/IEC 18004 is the international standard that specifies QR Code symbology. It covers data encoding, symbol formats, dimensions, error correction, decoding, print quality, and user-selectable parameters.

The current published edition is ISO/IEC 18004:2024. QR Code was developed in 1994 by a DENSO WAVE team led by Masahiro Hara, as documented in DENSO WAVE's development history. DENSO WAVE made the standardized specification available for broad use and states that it does not exercise the relevant patent rights for compliant QR Codes.

Quishing (QR phishing)

Quishing is phishing delivered through a QR code. The code can lead to a fake sign-in or payment page, or prompt a download designed to steal information.

Check the destination preview before opening it, treat unexpected QR codes like unexpected links, and examine stickers placed over public codes. The FBI's 2025 QR fraud alert advises people to avoid QR codes from unknown sources and to review requested permissions before granting access.

See the QR code scams and quishing guide.