PixelQR

How a QR code works

A QR code encodes text as a matrix of light and dark modules, with position patterns in the corners so a reader can locate it at any angle, and Reed-Solomon error-correction bytes distributed alongside the data so it stays readable even if part of it is damaged:

Text: "https://develotools.com"
→ byte mode + length indicator + UTF-8 bytes
→ + Reed-Solomon error-correction codewords
→ + position, timing and mask patterns
→ module matrix ready to print

This tool implements the QR encoding algorithm (ISO/IEC 18004) — including Reed-Solomon error correction and automatic mask selection — entirely in JavaScript, no external libraries, no server calls.

Frequently asked questions

How long can the text or URL be?

It depends on the error correction level chosen: up to ~170 characters with Low (L), or ~65 with High (H). If the content doesn't fit, the tool tells you instead of generating a broken code.

What do the L, M, Q and H error correction levels mean?

They indicate how much of the code can be damaged (a smudge, a tear, an overlaid logo) and still be readable: L ~7%, M ~15%, Q ~25%, H ~30%. More correction means a denser code with less data capacity.

Is the QR code generated in my browser or on a server?

100% in your browser, with a from-scratch implementation of the QR encoding algorithm (ISO/IEC 18004) — the content you type is never sent to any server.

Can I change the code's colors?

Yes, you can choose the module color and the background color. For the QR reader to work well, keep good contrast between the two.