5 min read
Updated: December 2024
What is Error Correction?
Error Correction Levels
How It Works
Choosing a Level
Error Correction & Logos
FAQ
Error correction is one of the most powerful features of QR codes. It allows QR codes to be successfully scanned even when part of the code is damaged, dirty, or obscured (like by a logo).
QR codes use Reed-Solomon error correction, the same technology used in CDs, DVDs, and satellite communications. It adds redundant data to the QR code that allows scanners to reconstruct missing or corrupted information.
QR codes have four error correction levels. Each offers a different balance between damage recovery and code size/capacity.
Clean environments, maximum data
General use, balanced
Outdoor use, some damage expected
Logo overlay, harsh conditions
| Level | Recovery | Size Overhead | Best For |
|---|---|---|---|
L - Low | ~7% | Lowest | Clean environments, maximum data |
M - Medium | ~15% | Moderate | General use, balanced |
Q - Quartile | ~25% | Higher | Outdoor use, some damage expected |
H - High | ~30% | Highest | Logo overlay, harsh conditions |
Here's a simplified explanation of how Reed-Solomon error correction works in QR codes:
Your data is split into small chunks called codewords (8 bits each).
Mathematical calculations generate additional 'check' codewords based on your data.
Data and error correction codewords are interleaved and encoded as the black/white pattern.
When scanned, the scanner uses the check codewords to verify the data.
If codewords are damaged, the scanner can mathematically reconstruct them from the redundant data.
Higher error correction = More redundant data = Larger QR code (or less capacity for your data)
Lower error correction = Less redundant data = Smaller QR code (or more capacity for your data)
Use this guide to select the appropriate error correction level for your use case:
| Level | Recommended Use | Why |
|---|---|---|
L (Low) | Digital displays, websites | No damage risk, maximum data capacity |
M (Medium) | General print materials | Default choice - good balance of capacity and recovery |
Q (Quartile) | Outdoor signage, packaging | Can handle weathering and moderate damage |
H (High) | QR codes with logos | Logo covers ~10-20% of code, needs maximum recovery |
Adding a logo to a QR code essentially "damages" it by covering some modules. Error correction allows the code to still work despite this intentional damage.
Our generator supports High error correction for logo overlays.
Create QR Code with LogoError correction allows QR codes to remain scannable even when partially damaged, dirty, or obscured. It adds redundant data that lets scanners reconstruct missing information.
Medium (M) is the default for most uses. Use High (H) if adding a logo. Use Low (L) only for digital displays where damage is impossible.
Yes, higher error correction adds more redundant data, which increases the QR code version (size/complexity). The same data with H level will create a larger code than with L level.
Yes, but use High (H) error correction to ensure scannability. The logo should cover no more than 10-15% of the code area and be placed in the center.
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