About QR Code Analyzer
QR Code Analyzer is a free online tool that instantly analyzes and displays technical details of a QR code, such as the error correction level, version, mask pattern, and encoding mode, simply by uploading a QR code image.
Information You Can Analyze
- Version: A number from 1 to 40 that determines the size of the QR code. The higher the version, the more data it can store.
- Error Correction Level: Four levels - L (7%), M (15%), Q (25%), H (30%). Indicates the ability to recover from dirt or damage.
- Mask Pattern: 8 types from 0 to 7. An XOR pattern applied to the data modules to improve reading accuracy.
- Encoding Mode: Data type such as numeric, alphanumeric, byte, or kanji.
- Module Structure Map: Displays the finder patterns, timing patterns, alignment patterns, format information, and data area in color-coded form.
Who It's For
Ideal for developers who need to verify QR code quality, designers who want to check whether a printed QR code was generated correctly, and students or engineers who want to learn how QR codes work. Everything runs in your browser, so images are never sent to a server.
Error Correction Levels (L / M / Q / H) in Detail
QR codes (JIS X 0510 / ISO/IEC 18004) use Reed-Solomon error correction. The error correction level indicates what proportion of the stored codewords can be recovered, and there are four levels: L, M, Q, and H. A higher level makes the code more resistant to dirt and damage, but it also adds more redundant error-correction codewords, so the same data may require a larger version (size).
| Level | Recoverable codewords (approx.) | Typical use |
|---|---|---|
| L (Low) | ~7% | When you want to maximize data capacity. Clean, low-wear environments. |
| M (Medium) | ~15% | Standard use. The most common choice for general QR code generation. |
| Q (Quartile) | ~25% | Somewhat harsh environments. Also handles small logo overlays. |
| H (High) | ~30% | Design QR codes with a center logo, or print that is likely to get soiled. |
The percentages are approximate ratios of recoverable codewords to total codewords. To learn how error correction works, see the article "How QR Code Error Correction Works". To experiment with how much you can obscure and still scan, the "QR Code Error Correction Tester" is handy.
Version (Size) and Module Count
QR code versions range from 1 to 40, and each step up adds four modules to each side. Version 1 is 21x21 modules and version 40 is 177x177 modules (version x 4 + 17). A higher version stores more data, but at the same physical print size the modules become finer, raising the requirements for scanning resolution and quiet-zone margins. This tool automatically detects and displays the version and module size of the uploaded code.
What Are Mask Patterns (0-7)?
A mask pattern regularly flips the data-area modules with an XOR operation, and the specification defines eight patterns numbered 0 to 7. By avoiding heavy black/white bias and arrangements that resemble finder patterns, masking improves scan reliability. During encoding, all eight patterns are evaluated and the one with the lowest penalty score defined by the specification is chosen. This tool reads the format information and shows which mask pattern number is applied.
Data Recovery and Damage Resistance
Even if some black modules are missing or some white modules are soiled black, the correct data can still be recovered as long as the damage stays within the error-correction budget. Reed-Solomon coding can correct both erasures (positions known to be unreadable) and errors (wrong values), and resistance scales with the redundancy of the chosen error correction level. Once damage exceeds the correction limit, scanning fails. When overlaying a logo, it is safest to verify against level H (~30%) so the obscured area does not exceed the level's tolerance. To simulate real damage or occlusion and find the limit, use the "QR Code Error Correction Tester"; to create a robust QR code from scratch, use the "QR Code Generator".