QR code stickers

A code is read by resolving its smallest square, so the two things that decide whether it scans are how far away the reader stands and how much you asked the code to carry. A short web address makes a coarse code that reads from across a room; a long one with tracking parameters on the end makes a dense code that struggles on a table.

Nothing under 50mm, and three shapes. Square, circle and rectangle are the cuts a code suits — a code is square, so a long bumper strip prints it at the strip's height and wastes the rest. And we do not sell a QR sticker below 50mm. A 40mm one is arithmetically possible with a short address, but it leaves nothing in reserve for vinyl, weather and an older phone, and a code that only works in good light is not a product.

You do not have to work it out. Choose a size and a destination and the configurator does the arithmetic: if the code would print too small to read reliably it says so, with the millimetres, and tells you whether to shorten the address or go up a size. A branded code is held to a stricter figure than a plain one, because the styling and the logo both spend from the same redundancy. The full arithmetic is here.

A plain code is square modules in black, or in any colour dark enough to scan. The colour costs nothing extra — it is the same ink on the same press, and we will not charge you for choosing it. What we do is check it: anything under 7:1 against white is refused at the field with the measured figure and the nearest darker shade of your own colour offered as a fix. That is a stricter line than text has to clear, because a phone camera has less to work with than an eye and a mid-tone brand colour prints lighter on vinyl than it looks on a backlit screen.

A branded code is the one with your logo in the middle, the modules drawn as rounded squares or dots, and the three corner squares softened and set in a second colour if you want one. It is $39 once per order, not per sticker — it is setup work, and the second sticker costs us no more than the first.

A branded code wants a short destination — around 58 characters. That is not a limitation of ours: some codes carry a pattern in the exact middle that a scanner uses to read them on an angle or a curve, and we will not print a logo over it. If your address is longer, a short link fixes it, and the page tells you so at the field rather than after you have paid.

A logo in a QR code is not an image pasted on top. It covers modules, and covered modules have to be recovered by the error correction, which has a fixed budget. So the middle is cleared to a plate whose size is worked out from that budget: we count the codewords the plate would cover and keep them well under what level H can rebuild, and the plate never touches the three corner squares, the alignment patterns or the timing line, whatever the budget says. If your logo will not fit inside that, the page says so rather than printing a code that scans on the desk and fails on a wet Tuesday.

The corner squares can be softened but not reinvented. A scanner finds a code at all by looking for the run of dark and light across those corners in a fixed 1:1:3:1:1 proportion. Rounding the corners keeps every module where a scanner looks for it. Circles do not — we drew them, tested them and dropped them, because a circle inscribed in the corner square misses the square's own corners. Novelty shapes are not on the menu for the same reason.