How a QR code stores your text
QR codes follow ISO/IEC 18004. The generator picks the smallest version that fits your content, from version 1 (21 × 21 modules) up to version 40 (177 × 177). Each version adds 4 modules per side, so the size is 17 + 4 × version. Your text is encoded as bytes, followed by Reed-Solomon error-correction codewords that let a scanner rebuild data from damaged or hidden areas.
Error-correction levels
The dropdown offers the four standard levels. A higher level restores more damage but spends more of the code on redundancy, so the same text needs a denser code.
| Level | Recovers up to | Max bytes (version 40) |
|---|---|---|
| L (Low) | about 7% | 2,953 |
| M (Medium, default) | about 15% | 2,331 |
| Q (Quartile) | about 25% | 1,663 |
| H (High) | about 30% | 1,273 |
A worked example
Encoding the 64-character address https://handybench.com/guides/how-to-make-a-professional-invoice gives four different codes. At L it fits version 4 (33 × 33 modules), at M version 5 (37 × 37), at Q version 6 (41 × 41) and at H version 7 (45 × 45). Same text, but the H code has more than 85% more modules than the L code, so each module prints smaller at the same physical size. For a printed flyer, M or Q is a sensible balance. Use H only if you plan to overlay a logo, and test the result.
Size and download options
The preview sizes are 128, 256 and 512 px, with a 2-module quiet margin. PNG is a fixed-size bitmap taken from the preview canvas. SVG is vector, so it scales to a poster or a business card with no blur; prefer it for print. ISO 18004 recommends a 4-module quiet zone, so leave white space around the code when you place it on a design.
Common mistakes
- Long URLs. Every extra character increases density. A short URL gives a simpler code that scans faster from farther away.
- Low contrast. Scanners need a dark code on a light background with strong contrast. Check colors with the contrast checker; inverted (light-on-dark) codes fail on some readers.
- Typos in the URL. The code is static, so a mistake is permanent once printed. Scan the exact file you will print before sending it to production.
- Printing too small. A common rule of thumb is a code at least 2 cm (0.8 in) wide for close-range scanning, and larger for dense codes.
The code stores your text directly, so it never expires. For connecting to a network see the WiFi QR code generator, for contact cards the vCard QR code generator, and for product labels the barcode generator.