How can QR code store so much data?

qr-code
Yellowmoon picture Yellowmoon · Oct 19, 2010 · Viewed 26.4k times · Source

Quick googling result that QR code can hold nearly 3kb (8 bit) data. But isn't it just using black/white dots to represent bits? If so there's no way that there's over 20,000 dots on a code.

So I'm obviously misunderstanding. Can someone explain how it works?

Answer

Mitch Wheat picture Mitch Wheat · Oct 19, 2010

QR Code data capacity

Numeric only:      Max. 7,089 characters 
Alphanumeric:      Max. 4,296 characters 
Binary (8 bits):   Max. 2,953 bytes 
Kanji/Kana:        Max. 1,817 characters

Version 40 is 177 x 177 and can store up to 7,089 numerics or 4,296 alpha-numerics (at lowest error correction)

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