QR Generator

QR Codes That Survive Contact With a Scanner

A QR code either reads or it does not, and the difference is rarely the software doing the scanning. It is usually margin, contrast, physical size, or a logo that ate more of the symbol than the code could spare. The controls here map onto those four failure modes.

Error correction is a budget

ISO/IEC 18004 defines four levels — L, M, Q and H — recovering roughly 7, 15, 25 and 30 percent of a damaged symbol through Reed-Solomon blocks. That redundancy is paid for in modules: the same URL at H produces a denser grid 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 was decorative and every code came out at H regardless of the setting; it now does what the label says.

Four modules of nothing

The blank margin around a QR code is part of the specification rather than a design flourish. Scanners use it to locate the boundary of the symbol. The standard asks for four modules of clear space on all four sides, and this generator was emitting two — a common reason codes read from a phone held close and fail from a metre away.

The full four modules are now baked into both the PNG and the SVG, so dropping the file into a layout cannot lose them. Do not crop them off afterwards, and do not lay a code directly over a busy photograph without a solid panel behind it.

Contrast, and which way round

Dark modules on a light background is what scanners are built to expect. The contrast ratio between your two colours is calculated as you pick them: below 3:1 you get a warning that the code will not scan, and if the foreground is lighter than the background you are told the code is inverted, because a large share of scanners refuse negative symbols. Aim for 7:1 or better. Pale brand colours on white are the most frequent cause of a code that works on the designer's screen and nowhere else.

Module shape and size

Three styles are available: classic squares, small dots, and larger circles. The three finder patterns in the corners stay square whatever you choose, since scanners lock onto those first and rounding them reliably breaks a code. Dots shrink each module slightly, reducing the dark area, which can cost you at small print sizes — if the code is going out small, stay with squares. There are no rounded-corner modules here, whatever the previous description implied.

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

The logo in the middle

An uploaded logo is placed over the centre at 18 percent of the code's width, on a small background pad. Every module underneath it is damage as far as the decoder is concerned, paid for out of the error-correction budget — which is why the interface asks you to move to level Q or H as soon as a logo is loaded. Test the finished code with two different phones before committing it to a print run.

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 recognised by the phone's own handlers, and anything else is displayed as plain text. Longer content means a bigger matrix, so shorten links before encoding rather than after. For linear retail and logistics symbols, Barcode Generator is the neighbouring page.