Matrix symbology
QR Code
QR Code is a two-dimensional matrix symbology that holds far more data than any linear barcode and is read by ordinary phone cameras, which is what makes it the format for consumer-facing links on packaging. It carries built-in error correction, so a symbol can be partially damaged and still decode.
Specification
These are the values the editor enforces while you design, not figures collected from elsewhere — the same numbers its quiet-zone and resolution checks run on.
| Property | Value | In context |
|---|---|---|
| Minimum X-dimension | 0.25 mm | 0.0098 in · 10 thou |
| Quiet zone | 4 modules | 1.00 mm at the minimum X-dimension |
| Dimensionality | Matrix (2D) | Requires an imager or camera |
QR Code at 203, 300 and 600 dpi
A printer can only place whole dots, and 0.25 mm is not a whole number of them at any of these resolutions. What changes is how much a single dot of rounding costs you as a share of the narrow bar.
| Resolution | Narrow bar in dots | Printed as | Rounding error |
|---|---|---|---|
| 203 dpi | 2.00 | 2 dots | 0% |
| 300 dpi | 2.95 | 3 dots | 2% |
| 600 dpi | 5.91 | 6 dots | 2% |
What QR Code encodes
Any text or URL, including numeric, alphanumeric and byte data, at capacities far beyond a linear symbology. Four error-correction levels trade capacity for damage tolerance — a higher level recovers from more damage but leaves less room for data at the same physical size.
Where it is used
- Consumer-facing links on packaging, from provenance information to reordering
- GS1 Digital Link, which carries a GTIN inside a resolvable web address
- Ticketing, payment and any context where the reader is a phone camera
Check digit
None, and it does not need one. QR Code uses Reed-Solomon error correction, which does more than detect an error — it reconstructs the missing data outright, up to the proportion of the symbol allowed by the chosen level.
How QR Code fails in practice
- Crowding the quiet zone. A QR code needs clear space on all four sides, and a symbol pushed against a package edge or a dark background is a common reason a phone will not lock on.
- Inverting the colours. Most readers expect dark modules on a light background, and a light-on-dark symbol fails on a meaningful share of devices.
- Encoding a very long URL, which raises the module count and therefore the physical size needed for each module to stay printable.
When to use something else
- Data Matrix — choose it instead when the symbol must be as small as possible and will be read by an industrial imager rather than a phone.
- Aztec — choose it instead when space is tight enough that the four-module quiet zone itself is the problem.
Questions about QR Code
- How small can a QR code be and still scan?
- It depends on the module count and the reader. More data means more modules, and each module still has to be printed wide enough to resolve — so a long URL at a fixed physical size is what usually pushes a symbol below what a camera can read.
- What is GS1 Digital Link?
- It expresses a GTIN as a resolvable web address, so one QR code serves both a consumer opening it on a phone and a system extracting the product identifier. It is central to the GS1 Sunrise 2027 move toward 2D codes at retail point of sale.