QR Code Fundamentals

인코딩 모드: 숫자, 영숫자, 바이트, 한자, ECI

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How QR codes encode data: five modes with different character sets and efficiency. When to use each mode and mixed-mode encoding.

  
  

    
  








  
  

    
    
      
      
  1. 
        Encoding Modes: Numeric, Alphanumeric, Byte, Kanji, and ECI
      
    2. 
      
      
  2. 
        Numeric Mode (0001)
      
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  3. 
        Alphanumeric Mode (0010)
      
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  4. 
        Byte Mode (0100)
      
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  5. 
        Kanji Mode (1000)
      
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  6. 
        ECI Mode (0111)
      
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  7. 
        Mixed-Mode Encoding
      
    8. 
      
      
  8. 
        Choosing the Right Mode
      
    9. 
      
      
  9. 
        Key Takeaways
      
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Encoding Modes: Numeric, Alphanumeric, Byte, Kanji, and ECI


QR codes support multiple encoding modes, each optimised for different character sets. Choosing the right mode affects how efficiently data is packed into the symbol, directly impacting the required version and physical size.


Numeric Mode (0001)


The most efficient mode, encoding digits 0-9 at approximately 3.3 bits per character. Three digits are packed into 10 bits. Use numeric mode for phone numbers, serial numbers, and numeric identifiers.


Capacity: Up to 7,089 characters at module count." data-category="QR Code Structure">Version 40, EC Level L.


Alphanumeric Mode (0010)


Encodes 45 characters: digits 0-9, uppercase A-Z, space, and symbols $ % * + - . / :. Two characters pack into 11 bits (5.5 bits each). This mode is ideal for URLs containing only uppercase letters.


Capacity: Up to 4,296 characters at Version 40, EC Level L.


Byte Mode (0100)


Encodes any 8-bit byte value (0-255), defaulting to byte mode encoding (Latin-1, 256 characters)." data-category="Standards & Specifications">ISO 8859-1. Each character uses exactly 8 bits. This is the most versatile mode and is used for URLs with lowercase letters, email addresses, vCard data, and UTF-8 encoded text.


Capacity: Up to 2,953 bytes at Version 40, EC Level L.


Kanji Mode (1000)


Encodes Shift JIS double-byte characters at 13 bits per character — more efficient than Byte mode's 16 bits for Japanese text. This mode was part of the original QR code design for its Japanese automotive origins.


ECI Mode (0111)


Extended Channel Interpretation allows specifying alternative character encodings beyond the default ISO 8859-1. ECI assignments include UTF-8 (ECI 26), various ISO encodings, and regional character sets.


Mixed-Mode Encoding


A single QR code can switch between modes within the same symbol. For example, a string like HTTP://EXAMPLE.COM/12345 can use Alphanumeric mode for the URL portion and Numeric mode for the digits, saving space. Each mode switch costs a 4-bit encoding mode." data-category="Encoding & Data">mode indicator plus a character count indicator.


Choosing the Right Mode


Most QR code libraries handle mode selection automatically. However, understanding modes helps you optimise data for smaller codes:


    

  • Use uppercase URLs to trigger Alphanumeric mode instead of Byte mode
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  • Separate long numeric segments (like phone numbers) for Numeric mode encoding
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  • For international text, ECI mode with UTF-8 is the standard approach
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Key Takeaways


    

  • Numeric mode: 3.3 bits/char — most efficient for digits only
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  • Alphanumeric: 5.5 bits/char — uppercase, digits, and a few symbols
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  • Byte: 8 bits/char — universal, handles any data
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  • Kanji: 13 bits/char — efficient for Japanese Shift JIS characters
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  • Mixed-mode encoding can combine modes to minimize QR code size
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