Measures the version from the string you encode and calculates how many millimetres you need, quiet zone included
| Item | Value | Assessment |
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Scanning succeeds or fails on whether the camera can tell each module apart as black or white. Printed at the same 25 mm square, version 2 (25 modules) gives a module of about 0.85 mm, while version 10 (57 modules) drops to about 0.38 mm. That is why the same printed size becomes harder to scan as you put more data in. When a code will not scan, suspect the module size before the printed size.
The standards (ISO/IEC 18004 and JIS X 0510) require a margin of four modules around the code. Scanners use it to work out where the code ends, so packing content right up against it lowers the read rate. It is the first thing people cut when a business card or flyer runs out of space, but cutting it has the same effect as shrinking the code. Every figure this tool reports includes the margin.
If you cannot make the printed size any bigger, the move is to put less data in so the version drops. For a URL, dropping tracking parameters or shortening the path can take the version down one or two steps. Each step down removes four modules from the side, so the module grows at the same printed size. Lowering the error correction level from H to M works in the same direction, at the cost of tolerating less dirt and damage.
When you export an image, how many pixels each module occupies decides the quality. If a module is not a whole number of pixels, resampling blurs the module boundaries. Aim for at least three to four pixels per module, and prefer dimensions where the module width comes out as a whole number. This tool reports the pixels per module at your chosen dpi so you can check.
A common rule of thumb is one tenth of the scanning distance. Read from 50 cm, that is about 50 mm; on a poster read from 2 m, about 200 mm. It is only a guideline, because the size you actually need depends on the version. The more modules a code has, the smaller each module becomes at the same printed size.
It is the blank margin required around a QR code. The standards (ISO/IEC 18004 and JIS X 0510) specify four modules on each side. Without it a scanner cannot tell where the code ends, and the read rate drops. Reserve space for the margin as well as the code itself.
No. Encoding and calculation happen entirely in your browser using JavaScript. Nothing you type is sent to a server.