Choosing QR Code Error Correction Levels
QR code error correction is a built-in feature that allows codes to remain scannable even when partially damaged or dirty. Understanding the four levels (L, M, Q, H) helps you choose the right balance between reliability and data capacity.
What is Error Correction?
Error correction in QR codes uses redundant data to reconstruct information if parts of the code are damaged, dirty, faded, or obscured. The QR code specification defines four error correction levels, each offering different amounts of redundancy and damage tolerance.
Higher error correction levels can recover from more damage, but require more space in the QR code (making it denser and potentially harder to scan). Lower levels create simpler codes but are less resilient to damage. Choosing the right level depends on your use case.
The Four Error Correction Levels
Level L (Low) - 7% Recovery
7% damage toleranceThe lowest error correction level. Can recover if up to 7% of the QR code is damaged or unreadable.
Best for:
- • Digital displays only (websites, presentations, screens)
- • Controlled environments where damage is unlikely
- • Very long URLs where you need maximum data capacity
- • Temporary uses (event badges, digital tickets)
Avoid for:
- • Any printed materials
- • Outdoor use
- • Long-term applications
Level M (Medium) - 15% Recovery
15% damage toleranceStandard error correction level. Can recover if up to 15% of the QR code is damaged. Good balance between reliability and simplicity.
Best for:
- • Indoor printed materials (flyers, brochures, posters)
- • Business cards (if not adding logo)
- • Product packaging in controlled environments
- • General-purpose QR codes
Default choice for most applications
Level Q (Quartile) - 25% Recovery
25% damage toleranceHigh error correction. Can recover if up to 25% of the QR code is damaged. Recommended for most professional applications.
Best for:
- • Outdoor signage and posters
- • Product labels that experience wear
- • Business cards (professional standard)
- • Manufacturing/industrial applications
- • Long-term installations
Recommended for most business use
Level H (High) - 30% Recovery
30% damage toleranceMaximum error correction. Can recover if up to 30% of the QR code is damaged. Required for logo placement.
Best for:
- • QR codes with embedded logos (MANDATORY)
- • Harsh outdoor environments
- • High-wear applications (equipment labels, tools)
- • Critical scans (payment codes, emergency info)
- • UV exposure, weathering, frequent handling
⚠️ Tradeoff: Creates denser QR codes
Quick Decision Guide
Which Level Should You Choose?
Choose Level H (30%) if:
- • Adding a logo to the QR code (non-negotiable)
- • Outdoor use with weather exposure
- • High-wear environment (manufacturing, shipping)
- • Critical applications (payments, access control)
Choose Level Q (25%) if:
- • Professional business cards
- • Product packaging
- • Outdoor posters/signs
- • You want extra reliability (good default choice)
Choose Level M (15%) if:
- • Indoor flyers, brochures, posters
- • Controlled environments
- • Standard applications without special requirements
Choose Level L (7%) if:
- • Digital-only display (never printed)
- • Maximum data capacity needed
- • Temporary/one-time use
Error Correction and Data Capacity
Higher error correction requires more redundant data, which reduces the capacity for your actual content. This creates a tradeoff:
| Level | Recovery | Approx. Capacity Loss | Visual Complexity |
|---|---|---|---|
| L | 7% | Baseline (most capacity) | Simplest |
| M | 15% | ~10% less capacity | More complex |
| Q | 25% | ~20% less capacity | Dense |
| H | 30% | ~30% less capacity | Densest |
💡 Practical Impact
If your URL is very long (100+ characters), using Level H instead of Level L might force the QR code to increase from Version 10 to Version 11, making it noticeably more complex.
Solution: Use URL shorteners to reduce data, then you can afford higher error correction without complexity penalty.
Use Case Recommendations
Business Cards
Recommended: Level Q (25%)
Business cards are handled frequently, kept in wallets (bending/wear), and sometimes printed on textured paper. Level Q provides reliability without excessive complexity for the small size.
Product Packaging
Recommended: Level H (30%)
Products experience shipping damage, shelf wear, handling, and potential scratching. Level H ensures scanability throughout product lifecycle. If adding company logo, Level H is mandatory.
Posters & Signage (Indoor)
Recommended: Level M (15%) or Q (25%)
Indoor posters are protected from weather but may fade over time. Level M is sufficient for short-term campaigns, Level Q for long-term installations or high-traffic areas.
Outdoor Signage
Recommended: Level H (30%)
UV exposure, rain, dirt, and temperature changes degrade outdoor QR codes. Level H provides maximum protection against environmental damage.
Digital Displays (Screens)
Recommended: Level L (7%) or M (15%)
Digital displays show perfect QR codes with no physical damage. Level L maximizes simplicity for easy scanning. Use Level M if you want some buffer against screen glare or brightness issues.
QR Codes with Logos
Required: Level H (30%)
Logos obscure 20-25% of the QR code. You MUST use Level H to compensate. Attempting logos with lower levels will result in unscannable codes.
Common Misconceptions
Myth: "Always use maximum error correction for safety"
Reality: Higher error correction makes QR codes denser and harder to scan. Use appropriate level for your use case. Over-engineering creates problems.
Myth: "Error correction protects against all damage"
Reality: Error correction has limits. If damage exceeds the recovery percentage (e.g., 35% damaged with Level H), the code becomes unscannable. It's not magical - it's mathematical redundancy.
Myth: "You can add logos at any error correction level"
Reality: Logos require Level H. Lower levels don't have enough redundancy to compensate for the obscured data. This is non-negotiable.
Testing Error Correction
You can test error correction by intentionally damaging a QR code:
Error Correction Test:
- Generate same QR code at different error correction levels
- Print all versions
- Cover increasing amounts with tape/marker (10%, 20%, 30%)
- Scan to see which levels still work
- Level L fails around 7-10% coverage, Level H works up to 30%
Note: Don't obscure the three corner positioning markers - these are critical for all levels.
Conclusion
Error correction is a powerful feature that ensures QR code reliability, but it's not one-size-fits-all. Match the error correction level to your specific use case:
- Digital only: Level L or M
- Standard indoor print: Level M
- Professional/outdoor: Level Q
- With logo or harsh conditions: Level H
When in doubt, Level Q is a safe default that provides good reliability without excessive complexity. Only use Level L for digital displays, and always use Level H when adding logos.
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