QR Generator

QR Codes That Survive Contact With a Scanner

A QR code either reads or it doesn't, and when it doesn't, the scanning software is rarely to blame. Usually it's the margin, the contrast, the physical size, or a logo that covered more of the symbol than the code could spare. The controls on this page deal with each of those.

Error correction is a budget

ISO/IEC 18004 defines four levels, L, M, Q and H, which recover roughly 7, 15, 25 and 30 percent of a damaged symbol through Reed-Solomon blocks. You pay for that redundancy in modules. The same URL makes a denser grid at H than at L, and a denser grid needs more physical room to stay readable.

M is the default and suits most screen and print work. Move up to Q or H when the code will be printed on something that gets handled, weathered or covered. Until this rebuild the selector did nothing and every code came out at H whatever you picked. It now does what the label says.

Four modules of nothing

The blank margin around a QR code is part of the specification. Scanners use it to find the edge of the symbol. The standard asks for four modules of clear space on all four sides, and this generator used to put out two. That's a common reason a code reads from a phone held close and fails from a metre away.

The full four modules are now built into both the PNG and the SVG, so you can't lose them when you drop the file into a layout. Don't crop them off afterwards, and don't put a code straight over a busy photograph without a solid panel behind it.

Contrast, and which way round

Scanners are built to expect dark modules on a light background. The tool calculates the contrast ratio between your two colours as you pick them. Below 3:1 you'll get a warning that the code won't scan. If the foreground is lighter than the background, it tells you the code is inverted, because a lot of scanners refuse negative symbols. Aim for 7:1 or better. Pale brand colours on white are the most common reason a code works on the designer's screen and nowhere else.

Module shape and size

You can choose classic squares, small dots or larger circles. The three finder patterns in the corners stay square whichever you pick, since scanners lock onto those first and rounding them reliably breaks a code. Dots shrink each module slightly, which reduces the dark area and can hurt at small print sizes, so if the code is going out small, stick with squares. Despite what the previous description implied, there are no rounded-corner modules here.

Output size sets the pixel dimensions, and the hint under the slider shows how many pixels each module gets. Two pixels per module is the minimum for screen use. For print, work backwards from physical size. A code needs to be roughly a tenth of its scanning distance in width, so a poster read from two metres wants a symbol of about 20 cm. Export the SVG for anything printed, since it scales without going soft.

The logo in the middle

An uploaded logo goes over the centre at 18 percent of the code's width, on a small background pad. To the decoder, every module underneath it is damage, and that damage comes out of the error-correction budget. That's why the interface asks you to move to level Q or H as soon as you load a logo. Test the finished code with two different phones before you send it to print.

The content is just text

There are no Wi-Fi or contact-card presets. You type what the code should contain and the scanning device decides what to do with it. A https:// address opens, a mailto: or tel: string is picked up by the phone's own handlers, and anything else is shown as plain text. Longer content means a bigger matrix, so shorten links before you encode them. For linear retail and logistics symbols, Barcode Generator is the neighbouring page.