QR Code Generator

How to use the QR code generator

Choose what the code should do, fill in the fields, and it redraws as you type. Everything happens in this browser — the encoding, the styling, your logo, every download — because there is no server call for any of it to make. That matters more than it sounds: people put Wi-Fi passwords and private links into these.

The symbol is a square grid of modules, and the tool picks the smallest grid your data fits — that is the version it reports, from 1 to 40. Version 1 is 21 modules across and holds a few dozen characters. Version 40 is 177 across. More data means more modules in the same printed square.

The panel that shows you the string

Under the preview is the literal text going into the symbol. Open it. It is the only way to catch a wrong digit in a phone number, a password mangled by escaping, or a link that turns out to point somewhere other than you intended — the symbol itself gives you no clue, because a wrong code looks exactly like a right one.

It also names the host a scanner will be sent to. If that host is a known link shortener, the tool says so, because a shortener puts a company you do not control back between your printed sign and where it goes.

Downloads are SVG, PNG and JPG. Take the SVG for anything headed to print: it is a true vector with no resolution of its own, so the same file is crisp on a business card and crisp on a shop window, and it is what a printer will ask you for. Export PNG at the final size rather than enlarging a small one.

What actually breaks when a QR code stops working

Search for whether QR codes expire and you will find a great deal of confident nonsense in both directions. The truth is narrow and worth getting right, because it decides which kind of tool you should be using.

A QR symbol is a printed representation of a string. There is no clock in it, no account behind it and nothing to renew. If the string is `https://example.com/menu`, the code will hand a phone that address in twenty years exactly as it does today.

So what expires?

The middle step. Most commercial generators produce what they call a dynamic code: the printed symbol contains their domain, and their server looks up where to forward you. That buys something genuinely useful — you can change the destination after printing — and it costs you control of the link.

That is not an argument that dynamic codes are bad. It is an argument that they are a subscription to somebody else’s infrastructure, and that a poster on a wall is a bad place to hold one. Vendors in this market variously deactivate codes when a trial ends, pause them at a monthly scan cap, or show the scanner an advertisement first.

• Direct code: the destination is in the symbol; nobody can switch it off.
• Direct code: you cannot change where it goes after printing.
• Redirect code: you can change the destination whenever you like.
• Redirect code: it works for exactly as long as that vendor lets it.

If you want both, there is a way, and it does not involve a QR vendor: encode a short path on your own domain, such as `example.com/go/menu`, and redirect it from your own site. You keep the ability to change the destination, and the only company that can take it away is you.

How big does a printed code need to be?

Almost every answer to this online is the same rule: make the code about a tenth of the distance it will be read from. A metre away wants roughly ten centimetres. It is a reasonable starting point and it is worth knowing where it comes from — which is nowhere.

That ratio appears in no standard. Not in ISO/IEC 18004, which specifies the symbol; not in DENSO WAVE’s technical guidance, from the company that invented the format; not in GS1’s application specifications. It is a vendor convention that everybody repeats because it is easy to remember.

The floor the rule leaves out

It is also incomplete in a specific way: it takes no account of how much data is in the code. A short link and a full contact card read from the same distance get the same answer from that rule, and they need very different sizes, because one is 25 modules across and the other might be 57.

The second floor comes from the press. DENSO WAVE’s guidance is that each module should get at least four printer dots, so the module can be reproduced cleanly rather than smeared shut by ink spread. That floor scales with the module count, and it is the one that binds on dense codes and cheap printers.

So the panel asks for both. Set the distance and the printer and it reports the binding figure, says which constraint set it, and adds the quiet zone on top so you know the space to actually leave on the page. Then print one and scan it from where people will stand, because paper, gloss, lighting and angle are not in anybody’s formula.

What a logo in the middle really costs

The standard explanation is that error-correction level H recovers 30 percent, so you can cover 30 percent of the code with a logo. It is repeated everywhere, it sounds like engineering, and it is wrong in a way that matters.

The 30 percent refers to codewords, not to area. A QR symbol is divided into eight-bit codewords, and Reed-Solomon correction is budgeted per block: each block can generally fix about half as many wrong codewords as it carries recovery codewords. Damage that lands unevenly across blocks can exhaust one while the overall area covered still looks modest.

One wrong module spoils its whole codeword, so a logo does not cost you its own area — it costs you every codeword it touches, plus whatever the printing blurs at the edges. And the finder patterns, timing patterns and format information are not protected by that budget at all; lose them and no error-correction level saves the symbol.

In practice this tool clears a hole of a quarter of the symbol’s width — about six percent of its area — keeps it centred so it can never reach a finder pattern, and forces level H whenever a logo is present. That is conservative on purpose, and it is still a thing to test on the finished print rather than on screen.

Colour, and the inverted code

Contrast is the other way styling breaks a code, and the tool reports the ratio live. Below about 3:1 misreads climb sharply on ordinary phone cameras. Dark modules on a light background is what every decoder is built around.

Inverting it — light modules on dark — is more interesting than it looks. The 2024 revision of ISO/IEC 18004 explicitly permits reflectance reversal, so an inverted code is a conforming QR code. But neither Apple nor Google publishes any guarantee that their cameras decode one, and the widely used open-source decoder only retries inverted when an option is switched on. Permitted by the standard, and still a gamble in print.

The formula, worked line by line

Two independent floors decide the printed size, and they move in opposite directions. One follows the reading distance and ignores the data; the other follows the data and ignores the distance. The size to print is whichever asks for more.

modules per side  = 4 × version + 17

width from distance = reading distance ÷ 10
width from printer  = modules × dots per module ÷ dpi

print width = the larger of the two
space to leave = print width × (modules + 8) ÷ modules

The four extra modules of quiet zone on each side are why the last line exists: the symbol is `modules` wide, but the block of space it needs on the page is eight modules wider than that.

A worked case. A 1,200-byte contact card at level M makes a version 27 symbol, so 4 × 27 + 17 = 125 modules a side. Read from 30 cm, the distance rule asks for 30 mm. At 300 dpi the printer asks for 125 × 4 ÷ 300 inches, which is 42 mm. The printer wins, and a code printed to the rule alone would have been a third too small.

Dots per module is four, from DENSO WAVE’s reproduction guidance. Below that, ink spread starts closing the gaps between modules, and the symbol degrades in a way no error correction was designed to absorb.

A page for each thing a code can do

The symbol is the same either way — what changes is the string inside it, and every format has its own way of going wrong. Each page opens this tool on that type and explains the format it writes, with a worked example you can read.

Questions people ask