Glossary
Timing pattern
The timing patterns are the alternating black-and-white lines running between the finder patterns, one horizontal and one vertical. They tell the decoder the module pitch, so it knows where each cell boundary falls.
What they do
After the finder patterns establish the corners, the decoder still needs to know the exact grid spacing. The timing patterns are a run of alternating modules on row 6 and column 6, functioning as a ruler.
They are why a code can be photographed slightly out of square and still be sampled correctly: the decoder counts the alternations rather than assuming an even division.
Design implications
Heavy styling that merges adjacent modules — very organic or "liquid" module shapes, or aggressive rounding — damages the timing pattern first, because it depends on adjacent modules being visually distinct. A style that keeps a visible gap between modules preserves it.
Related
- Finder pattern — The three large concentric squares in the corners of a QR code are finder patterns. A scanner locates them first to work out where the code is, how big it…
- Alignment pattern — Alignment patterns are the small 5 × 5 concentric squares scattered through larger QR codes. They let a scanner correct for perspective distortion when…
- Mask pattern — A mask pattern is one of eight XOR patterns applied to a QR code's data area to avoid large blocks of one colour and false finder-like shapes. The encoder…