This QR code checker reads a code from an image and analyzes how it was built: its version and size in modules, the error correction level, the mask pattern, the quiet zone around it, the contrast between its dark and light squares, and what it contains. Each measurement gets a pass, warning or fail, with the fix.
Use it before you print a code, or to find out why an existing code scans badly. The analysis runs in your browser, so the image never leaves your device.
What the QR code checker measures
| Check | What it means | Good value |
|---|---|---|
| Version and size | QR codes come in 40 versions, from 21 x 21 modules (version 1) to 177 x 177 (version 40). More content needs a higher version, which means smaller squares at the same print size. | Version 1 to 6 for most links |
| Error correction | Extra data that lets a scanner rebuild a damaged code. Level L recovers about 7%, M about 15%, Q about 25% and H about 30%. | M for plain codes, Q or H with a logo |
| Mask pattern | One of eight patterns the generator lays over the data to avoid large blocks of one color. The checker reads it from the format information next to the corner squares. | Any, the generator picks it |
| Contrast | The brightness ratio between the dark and light squares, measured from your image. | 4.5 : 1 or more |
| Colors | Whether the code is dark on light, or inverted (light on dark). | Dark on light |
| Quiet zone | The empty margin around the code, in modules. The QR standard (ISO/IEC 18004) asks for 4. | 4 modules or more |
| Print size | The smallest width that scans from your chosen distance, from the 10 to 1 distance rule, raised for dense codes. | About 1 cm per 10 cm |
How to use the results
A fail means many phones will struggle. Fix it before printing: usually that means more contrast, a wider quiet zone, or a sharper source image. A warning means most modern phones will cope, but older phones, dim rooms or long distances may not. Info lines describe the code without judging it.
When you check a cropped screenshot, the quiet zone can look smaller than it really is, because the crop cut it off. Check the file you will actually print, or a photo of the printed code, for a true measurement.
Error correction and logos
A logo in the middle of a QR code hides data, and error correction is what rebuilds it. A logo that covers 10% of the code is safe at level Q or H and risky at L. If the checker shows level L or M on a code with a logo, remake it at a higher level with the QR code with logo generator. For the reasons logo codes fail, see why logo QR codes fail to scan, and for the levels themselves, QR code error correction levels.
Checking a code that will not scan at all
The checker needs to find the code first. If it says no QR code was found, the image is probably too blurred or the code is damaged. Try the blurry QR code reader for soft photos and QR code repair for torn or covered codes, then follow QR code not scanning for everything else. To check how different phones handle hard codes, use the QR code test sample codes.
Is the link safe?
This checker looks at how a code is built, not where it leads. A perfectly built code can still point to a fake login page. For links, press "Check the link is safe" after the analysis, or open the safe QR code scanner, which looks for the warning signs used in QR phishing.
Frequently asked questions
How do I check if a QR code works before printing?
Run the PNG or PDF export through this checker and fix any fail. Then print one proof at the real size, scan it with at least two phones from the distance people will stand, and confirm the link opens the right page. The full routine is in how to test a QR code before printing.
How can I tell which error correction level a QR code uses?
The level is stored in 15 format bits beside the corner squares. This checker reads those bits from your image and matches them against the 32 valid combinations, so it can tell you the level and mask even when a few bits are damaged.
What is a good contrast for a QR code?
Aim for 4.5 : 1 or more between the dark and light squares, with the dark color on the light background. Black on white is about 21 : 1. Pale brand colors often fall below 3 : 1, which is where scanners start to fail.
Does the checker upload my image?
No. The image is read and measured in your browser. Nothing is sent to our server, and the result disappears when you leave the page.
Can it check barcodes too?
This page analyzes QR codes. To check a retail barcode number, use the EAN-13 check digit calculator or read the barcode with the online barcode scanner.
Found a wrong measurement? Report a bug. Changelog: 31 October 2026, page published: version, error correction, mask, contrast, colors, quiet zone, sharpness and print size.