How QR codes work
A QR (Quick Response) code is a two-dimensional barcode invented by Denso Wave in 1994. Because it stores data both horizontally and vertically, it holds far more than a classic barcode in a small square, and any modern phone camera can read it. The code is a grid of dark and light modules: the smallest size, version 1, is 21×21 modules, and each version adds 4 modules per side up to version 40 (177×177). This generator picks the smallest version that fits your text automatically and shows it below the preview.
The codes made here are static: your text is encoded directly into the image. There is no tracking redirect in between, so the code cannot expire or be switched off by a third party.
Choosing an error correction level
QR codes contain redundant data (Reed–Solomon error correction) so they stay readable when part of the code is dirty, damaged or covered. A higher level is more robust but needs more modules, so the code becomes denser.
| Level | Recoverable data (approx.) | Max. bytes (version 40) | Good for |
|---|---|---|---|
| L | ~7% | 2,953 | Screens and clean surfaces |
| M | ~15% | 2,331 | General print (default) |
| Q | ~25% | 1,663 | Outdoor signs, industrial use |
| H | ~30% | 1,273 | Codes with a logo in the middle |
Tips for a code that scans reliably
- Keep a blank margin (the quiet zone) around the code. This tool adds the standard 4-module margin automatically.
- Shorter content means fewer, larger modules. Print long URLs bigger, or shorten them first.
- Use a dark code on a light background. Some scanner apps cannot read inverted (light-on-dark) codes, and low-contrast color pairs fail more often.
- For print, download the SVG: it is a vector image and stays sharp at any size.
- Always test the final printed code with a couple of different phones before mass printing.
Frequently asked questions
Do the QR codes expire?
No. The text or URL is stored directly in the code without any redirect service, so it keeps working forever. It only stops working if the page it links to goes offline.
Can I use the QR codes commercially?
Yes. Denso Wave, the inventor of the QR code, has stated that it does not exercise its patent rights, so you can use the generated codes freely, including in print and on products. “QR Code” is a registered trademark of Denso Wave.
How much text fits in a QR code?
This tool stores text as UTF-8 bytes. The largest QR code (version 40) holds up to 2,953 bytes at level L and 1,273 bytes at level H. Plain ASCII uses 1 byte per character, accented letters such as é use 2 bytes, most CJK characters 3 bytes and emoji 4 bytes. Codes near the limit are very dense and hard to scan, so keep content short.
Is my text sent to a server?
No. The QR code is drawn in your browser with JavaScript, and the PNG and SVG files are created locally. Nothing you type is uploaded or stored.