QR Code Fundamentals

오류 수정 레벨 L, M, Q, H: 선택 방법

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Understanding error correction levels and their trade-offs. When to use L (7%), M (15%), Q (25%), or H (30%) recovery.

  
  

    
  








  
  

    
    
      
      
  1. 
        Error Correction Levels L, M, Q, H: How to Choose
      
    2. 
      
      
  2. 
        The Four Levels
      
    3. 
      
      
  3. 
        How Error Correction Works
      
    4. 
      
      
  4. 
        Decision Framework
      
    5. 
      
      
  5. 
        The Capacity Trade-off
      
    6. 
      
      
  6. 
        Key Takeaways
      
    7. 
      
    

  









  
  

  
  

    
    

      
Error Correction Levels L, M, Q, H: How to Choose


Every QR code includes Reed-Solomon error correction data that enables recovery from damage, dirt, or partial obstruction. The four error correction (EC) levels offer different trade-offs between resilience and data capacity.


The Four Levels






Level
Recovery Rate
Use Case






L (Low)
~7%
Digital screens, controlled environments




M (Medium)
~15%
General purpose, default for most applications




Q (Quartile)
~25%
Outdoor signage, rough handling




H (High)
~30%
Industrial, logo embedding, harsh environments






How Error Correction Works


When a QR code is generated, the encoder adds redundant error correction codewords alongside your data. At scan time, the decoder uses these codewords to detect and correct errors. The more EC codewords, the more damage the code can survive — but the less space remains for your actual data.


At EC Level L, roughly 7% of codewords are correctable. At Level H, approximately 30% can be recovered. This means a module count." data-category="QR Code Structure">Version 5 QR code at Level L can hold 154 bytes, but the same version at Level H holds only 74 bytes.


Decision Framework


Choose Level L when the QR code is displayed on a digital screen (phone, monitor, TV) with no risk of physical damage. This gives you maximum data capacity and the smallest possible version.


Choose Level M for general print applications: business cards, flyers, product labels. Level M is the default in most generators and provides a good balance.


Choose Level Q when the QR code will face moderate physical stress: outdoor signage, warehouse labels, or codes that might get scratched or stained.


Choose Level H for logo embedding (the logo covers and "damages" modules), industrial environments, or any scenario where the code may sustain significant damage.


The Capacity Trade-off


Higher EC levels reduce data capacity substantially. If your data barely fits at Level M, switching to Level H may force the generator to use a larger version, increasing the physical size of the code. Always test with your actual data.


Key Takeaways


    

  • Four levels: L (7%), M (15%), Q (25%), H (30%) error recovery
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  • Higher EC = more damage resistance but less data capacity
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  • Level M is the safe default for most printed QR codes
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  • Level H is essential when embedding a logo
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  • Always verify your data fits at the chosen EC level before printing
    •