Is Data Matrix smaller than a QR code?

For the same data, generally yes. It also requires a quiet zone of a single module against QR Code's four, so the difference in total footprint is larger than the difference in the symbols themselves.

Matrix symbology

Data Matrix

Data Matrix is a two-dimensional symbology built for marking very small items, and it reaches a smaller physical footprint than QR Code for the same data. It needs a quiet zone of only one module, which is why it appears on electronic components, surgical instruments and pharmaceutical packaging.

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.

Data Matrix specification: minimum X-dimension, quiet zone and dimensionality
Property	Value	In context
Minimum X-dimension	0.25 mm	0.0098 in · 10 thou
Quiet zone	1 modules	0.25 mm at the minimum X-dimension
Dimensionality	Matrix (2D)	Requires an imager or camera

Data Matrix 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.

Data Matrix narrow bar in printer dots at 203, 300 and 600 dpi
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 Data Matrix encodes

Any text, with the modern ECC 200 form using Reed-Solomon error correction throughout. Capacity is high for the size, and the symbol grows in discrete steps rather than continuously as data is added.

Where it is used

Direct part marking on components, tools and instruments
Pharmaceutical serialisation, usually as GS1 DataMatrix carrying Application Identifiers
Small-item labelling where no linear symbology fits

Check digit

None. Like QR Code, Data Matrix uses Reed-Solomon error correction, which reconstructs damaged modules rather than merely detecting that something is wrong.

How Data Matrix fails in practice

Printing below the resolution the printer can hold. A 2D symbol degrades differently from a linear one — modules merge rather than bars thinning — and the failure is abrupt rather than gradual.
Insufficient contrast on a marked surface. Direct part marking relies on the imager seeing a reliable difference between marked and unmarked material, which is a lighting problem as much as a printing one.
Confusing plain Data Matrix with GS1 DataMatrix. The second carries Application Identifiers and is what a regulated supply chain expects.

When to use something else

QR Code — choose it instead when a consumer will scan it with a phone camera, which handles QR more reliably.
Aztec — choose it instead when you need to remove the quiet-zone requirement entirely.

Questions about Data Matrix

Is Data Matrix smaller than a QR code?: For the same data, generally yes. It also requires a quiet zone of a single module against QR Code's four, so the difference in total footprint is larger than the difference in the symbols themselves.