2D Data Matrix code generator

Data Matrix packs data into a square (or occasionally rectangular) grid of modules, surrounded on two sides by a solid L-shaped finder pattern and on the other two by an alternating light-dark clock track. The scanner uses the L to find the symbol and the clock track to work out how many modules it contains, which is why Data Matrix tolerates being photographed at an angle far better than a linear barcode.

Modern Data Matrix means ECC 200, the variant with Reed–Solomon error correction. It can rebuild the payload from a symbol with roughly a quarter of its area damaged, which is what makes it usable for direct part marking — dot peening, laser etching or chemical etching straight onto metal, where the mark is never as clean as ink on paper.

Its real advantage is size. A short serial number fits into a 12 × 12 module symbol that can be printed at two or three millimetres square and still scanned by a decent imager. Nothing else in common use is that small, which is why it ends up on circuit boards, surgical instruments and the tiny panel of a medicine carton where the EU Falsified Medicines Directive requires a unique identifier.

Every ECC 200 symbol has the same frame. The left and bottom edges are solid dark lines that form the L-shaped finder pattern; the top and right edges alternate dark and light modules to form the clock track, also called the timing pattern. Inside the frame, each 8-bit codeword occupies a block of eight modules, and the data codewords are followed by Reed–Solomon error correction codewords.

From 32 × 32 upwards the symbol is split into several data regions, each with its own finder and clock edges, so that a scanner can keep track of the grid across a large mark. A 144 × 144 symbol is 36 regions of 22 × 22 data modules. Square symbols run from 10 × 10 to 144 × 144 modules in 24 sizes; six rectangular sizes from 8 × 18 to 16 × 48 fit narrow strips. Every size has an even number of rows and columns.

This generator always chooses the smallest square size that holds your text. The capacities below are maxima for data of a single type; mixed content fits somewhat less.

Both are square 2D codes with Reed–Solomon error correction that read at any angle. Data Matrix is the smaller of the two for short data — a twelve-character serial number fits in a 16 × 16 Data Matrix but needs a 21 × 21 QR code — and it asks for a one-module quiet zone where QR asks for four. That is why industry marks parts, instruments and medicine packs with Data Matrix. QR codes have selectable error correction levels and near-universal support in phone camera apps, which is why anything aimed at the public uses QR.

Data Matrix only needs a one-module quiet zone, but it does need the contrast. On metal, the readable ones are almost always the ones where the marking process produced a genuine light-dark difference under the imager’s illumination rather than a shallow scratch.

Print or mark it square. Unlike a linear barcode, a Data Matrix distorted along one axis quickly stops decoding, because the clock track no longer matches the module grid the scanner reconstructs. Export SVG and scale proportionally.