What a QR code is
A QR code is a two-dimensional barcode: a grid of dark and light squares (modules) that stores text. The three corner squares tell a camera where the code is and how it is rotated; built-in error correction reads through smudges. It is an open standard (ISO/IEC 18004).
How to use the generator
- Text or URL — a web address, a message, a Wi-Fi login or any format below. Start links with
https://so phones offer to open them. - Error correction — M for most uses; H if a logo will cover the middle or the code lives outdoors or on packaging.
- Download size — the pixel size written into the SVG. SVG is vector and prints sharp at any size; the number is only the default in an editor.
Printing it so that it scans
- Size: a code reads comfortably from about ten times its width — a 2 cm code from 20 cm; a poster read from 3 m needs about 30 cm.
- Quiet zone: the standard requires a blank margin four modules wide. The SVG includes it; do not crop it.
- Contrast: dark modules on a light background. Inverted and pastel codes fail on many scanners.
- Test with two phones before a print run.
How the code is built
The text becomes UTF-8 bytes in byte mode, so any character — accented letters, Arabic, Chinese, emoji — works. The smallest version that holds those bytes at the chosen level is picked, Reed–Solomon error-correction codewords are added, and everything is placed in the grid in a zigzag. The eight standard masks are tried and the one with the fewest scanning hazards is kept.
Worked example
https://calcworthy.com is 22 bytes; with the 4-bit mode indicator and 8-bit length it needs 188 bits. Version 1 at level M offers 16 data codewords (128 bits), too small, so the generator steps up to version 2: 25 × 25 modules, 44 codewords — 28 data, 16 error correction. The 7 spare data bytes hold padding, hence "7 bytes of room left".
Error-correction levels
| Level | Damage recoverable | Typical use |
|---|---|---|
| L | about 7% of codewords | Screens, large codes, maximum capacity |
| M | about 15% | Everyday printing — the usual default |
| Q | about 25% | Industrial labels, small codes on packaging |
| H | about 30% | Logo in the center, outdoor and dirty surfaces |
Error correction costs capacity: the same text at level H can need a version two or three steps larger than at L.
Capacity in byte mode, versions 1–10
An ASCII character is one byte, most accented letters two, Chinese and Japanese characters three, emoji four. Capacity grows up to version 40 (177 × 177 modules): 2,953 bytes at level L.
| Version | Modules | L | M | Q | H |
|---|---|---|---|---|---|
| 1 | 21 × 21 | 17 | 14 | 11 | 7 |
| 2 | 25 × 25 | 32 | 26 | 20 | 14 |
| 3 | 29 × 29 | 53 | 42 | 32 | 24 |
| 4 | 33 × 33 | 78 | 62 | 46 | 34 |
| 5 | 37 × 37 | 106 | 84 | 60 | 44 |
| 6 | 41 × 41 | 134 | 106 | 74 | 58 |
| 7 | 45 × 45 | 154 | 122 | 86 | 64 |
| 8 | 49 × 49 | 192 | 152 | 108 | 84 |
| 9 | 53 × 53 | 230 | 180 | 130 | 98 |
| 10 | 57 × 57 | 271 | 213 | 151 | 119 |
Special formats phones understand
- Wi-Fi login:
WIFI:T:WPA;S:NetworkName;P:password;;— the phone offers to join. UseT:nopass;for an open network; escape; , : \with a backslash. - Email:
mailto:name@example.com?subject=Hello - Phone call:
tel:+12125551234; text message:SMSTO:+12125551234:Your message - Map location:
geo:40.7128,-74.0060 - Contact card: a vCard —
BEGIN:VCARD,VERSION:3.0, lines likeN:Last;First,TEL:+1...,EMAIL:..., thenEND:VCARD. Every field enlarges the code.
Privacy and lifetime
Your browser encodes the text and never sends it anywhere, so the generator is safe for Wi-Fi passwords and private links. A code that contains the text directly, as these do, cannot expire; only codes that point to a third-party redirect service die when that service does. For a strong Wi-Fi password, try the password generator.
Frequently asked questions
Is this QR code generator really free, with no expiry?
Yes. The code is made in your browser with no account, watermark or limit, and because the text is stored inside the code itself there is no redirect server to switch it off.
How big should I print a QR code?
About one tenth of the scanning distance: 2–3 cm (an inch) for a card read at arm’s length, 10 cm for a shop window, 30 cm or more for a poster read across a room.
Can I put a logo in the middle?
Yes, at level H, if the logo covers at most about a fifth of the area and stays clear of the corner squares and the small alignment square. Test on several phones: the logo uses up the margin that would otherwise cover print defects.
Which file format should I use?
SVG for anything printed or resized: it is vector, stays sharp at any size and is accepted by design software, Word and label printers. If an app insists on PNG, open the SVG in an image editor and export it.
Last updated: October 9, 2026