QR code with a logo: error correction, size and contrast
A QR code still scans with a logo in the middle thanks to error correction: extra data that lets a reader rebuild the content when part of the code is dirty or covered. The squares your logo hides use up part of that margin. So with a logo, raise error correction to H (about 30%), keep the logo small, and make the dots much darker than the background. Staycode raises error correction to H when you add a logo, and its scan check calls a brightness contrast under 2:1 "No scan" and under 4:1 "Check".
Which error correction level should I use?
There are four levels. Higher levels survive more damage but need more modules for the same content. Summarizing DENSO WAVE, the company that created the QR code (checked October 14, 2026):
| Level | Can restore | Typical use according to DENSO WAVE |
|---|---|---|
| L | about 7% | Clean environments, lots of data |
| M | about 15% | The most commonly used level |
| Q | about 25% | Places where codes get dirty, such as factories |
| H | about 30% | Places where codes get dirty, such as factories |
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The percentage is the share of codewords that can be restored. One hidden module can touch more than one codeword, so a logo that covers exactly that percentage leaves no room at all. This generator switches to H when you add a logo and tells you so, and switches back when you remove it.
How big can the logo be?
Small enough that the area it clears stays under about a third of the error correction margin, which is about 10.5% at level H. Past that line, the scan check shows a warning. Here is https://example.com/menu at level H with different "Logo size" settings (logo width as a share of the code width):
| Logo size | Area cleared | Scan check |
|---|---|---|
| 10 to 13% | 3.0% | Logo rule passes |
| 14 to 20% | 5.8% | Logo rule passes |
| 21 to 27% | 9.6% | Logo rule passes |
| 28 to 30% | 14.4% | Check: the logo leaves almost no room for error correction |
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Modules are cleared whole, so the area climbs in steps. On a denser code (a longer link, 49×49 modules) the rule passed up to 28% and warned from 29%. The default logo size is 20%. If you set error correction back to L or M yourself, you get a warning even with a small logo.
"Clear dots behind the logo" (on by default) empties the modules around the logo so it does not blend into the dots. If your logo has transparent edges, "Put a background under the logo" makes it crisper.
Picking colors: the 2:1 and 4:1 rules
Phone cameras tell dots from background by brightness, not hue. The generator computes the brightness contrast between dot color and background: under 2:1 is "No scan" before the image is even read, and 2:1 to 4:1 is "Check". Examples on a white background unless noted:
| Dot color | Background | Contrast | Scan check |
|---|---|---|---|
#1e3a8a navy | #fef3c7 cream | 9.3:1 | Contrast passes |
#2e7d32 dark green | white | 5.1:1 | Contrast passes |
#777777 gray | white | 4.4:1 | Contrast passes |
#8a8a8a light gray | white | 3.4:1 | Check |
#ff8a00 orange | white | 2.3:1 | Check |
#ffd400 yellow | white | 1.4:1 | No scan |
| white dots | black | inverted | No scan |
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For gradients, the lightest end color is measured; separate eye colors are measured on their own. Light dots on a dark background are treated as "No scan" regardless of contrast, because most phone cameras cannot read them.
How the scan check decides
- Rules first: contrast under 2:1, or inverted colors, is "No scan" straight away.
- Read the image: the same image you download is converted to gray and read eight times at different sizes and blur levels.
- Scans: only when what was read matches your content character for character and no rule is triggered (contrast under 4:1, a large logo, a logo with L or M, or a quiet zone under 4 modules).
- Check: if it reads but a rule is triggered. In that case the check never shows the reassuring "it matches" message.
Even when the stamp says it scans, print quality, light and camera can change the real result. Scan a test print with your phone, and see QR code print size for sizing. Add a logo on the Logo tab of the QR code generator; the file stays on your device.
Sources
- DENSO WAVE: Error correction feature (Last checked October 14, 2026)