QR Code Validator

This one checks five things, all read off the image: whether the symbol decodes at all, the contrast between the two colours actually in the artwork, the quiet zone the file carries, the pixels per module, and the error-correction level stored in the code's own format information.

Because this is perfect light at full size and a shelf is neither. The gap is spent on printed size, paper reflectance, ink spread, glare and reading distance - none of which a file can show. Check the placed size in millimetres and print a proof on the real stock.

No. Error correction recovers damaged modules inside the data area after the symbol has been located. A missing quiet zone stops it being located in the first place, so there is nothing for the recovery to repair. The four-module margin has to come from the layout.

Level H, which recovers 30%, whenever a logo sits over the centre. Level M, recovering 15%, is fine for a clean code in a controlled setting and keeps the symbol smaller. Q is the middle ground for codes on packaging or anywhere the surface gets scuffed.

Four or more in the exported file keeps module edges hard through a resize, a compression pass or a reprint. Two or three still decodes on screen but leaves nothing in reserve. Below two, regenerate the code at a larger size rather than upscaling the file you have.

Not directly - a browser cannot rasterise an SVG without being told a size, so export it to PNG at the width you intend to print and validate that. The contrast and error-correction findings apply to the vector original; the pixels-per-module figure describes only the raster you exported.

No. It decodes the payload and reports it, but it never visits the destination - nothing here makes a network request. Copy the decoded string into a browser yourself and confirm the page loads, uses HTTPS, and is not a redirect that a previous campaign has retired.

Four modules of flat, light margin on all four sides, which is what ISO/IEC 18004 specifies. Many decoders manage on two in good conditions, which is why a short margin rarely shows up on screen - and why it is the first thing to cost a scan once the print or the background is poor.

Because the plain decode failed and the modules had to be filled out to their cells first. Rounded, dotted and other decorative modules put roughly half the ink of a square module into each cell, and a decoder hunting the 1:1:3:1:1 finder ratio reads exactly that ink. Size such codes generously.

If it decodes, yes, and the report describes the damaged file rather than the original. If it does not decode, that is a finding in itself: a code a decoder cannot find in a clean digital image will not be found on a shelf either.

Indirectly, from the payload. A dynamic code carries a short link to a redirect service, so its decoded content is a short URL on a provider's domain rather than your own destination. A static code carries the destination itself and never expires or changes.