QR Code Validator
Upload a code and get measured answers rather than a tick: how many modules of quiet zone it has, what the contrast actually is, which error-correction level it carries, how much a logo covers. Test it here before you commit it to five thousand flyers.
Drop your QR code here
or click to choose one — PNG, JPG, WebP, GIF or BMP.
The artwork you are about to print, a screenshot, an export from anywhere.
Why a tick is not an answer
Most code checkers tell you whether the code scanned on their machine. That is the least interesting thing about it, because a code that scans from a clean file on a desktop can still fail on a menu in a dim restaurant, on a window in sun, or once a printer has spread the ink a little. What decides that is how much margin the code has, and margin is a number.
So every check here reports the measurement and the threshold it is being held to. Four modules of quiet zone is the standard; yours might be 1.8. Contrast stops working below 4:1; yours might be 4.3, which passes and leaves nothing spare. A logo covering 7% of the area is a different proposition from one covering 19%. You can act on those. You cannot act on a green tick.
What each check is measuring, and where the number comes from
| Check | How it is measured | The threshold, and why |
|---|---|---|
| Decodes | The same two-pass ZXing configuration the generator uses to check its own output | Pass or fail. Everything else depends on it |
| Quiet zone | Clear rows and columns outside the code, divided by the module size — so the answer is in modules, the unit the standard uses | Four. With none, the same code stops scanning as soon as it sits on a dark background |
| Contrast | The mean colour of the dark modules against the mean colour of the light ones, as a WCAG ratio | 4:1 floor, 7:1 comfortable. Measured: 4.06:1 decoded, 4.00:1 did not |
| Logo | The area inside the code that is neither ink nor background, and whether it sits in the middle | No fixed limit — the honest answer is whether it still decoded |
| Destination | Properties of the URL text: scheme, shortener, an @ before the host, a punycode name | Flags, not a verdict on trust |
The module count is worked out rather than guessed. A finder-pattern centre sits three and a half modules in from its corner, so the two centres along one edge are n − 7 modules apart; with W the code's width in pixels and D that distance, n = 7W / (W − D). On real renders that recovers 21, 25, 29, 69 and 101 modules to the second decimal, which is what makes the quiet zone measurable in modules instead of pixels — and pixels are the wrong unit, because the same four modules is a different pixel count at every size.
What it will not tell you
Three things, and they matter as much as the checks.
- Whether the destination is safe. A code pointing at a real domain over https with no shortener passes every flag here and can still be a page collecting card details. The flags narrow the field; they do not clear it.
- How big it will be in print. An image has pixels, not millimetres. The module size in millimetres is shown for a 30 mm width as a reference point, but what decides legibility is the size you actually print at — keep a module at or above about 0.4 mm.
- Whether your printer and your customers' phones will agree with it. Nothing measured from a file substitutes for printing one on the real stock and scanning it at the distance people will stand.
What crosses the network
Nothing of yours. This page holds no fetch, no XMLHttpRequest, no sendBeacon and no form, so the image has no route off your machine; it is read with FileReader, drawn onto a canvas in your tab, and measured there. The only things fetched are the decoder library from jsDelivr — a static file, identical for every visitor — and this site's own header, fonts, analytics and ad script. That matters more here than usual, because the codes people most want to check before printing are the ones carrying a payment address or an internal link.