What Is A QR Code? | Basics Of 2D Codes | Barcode Information & Tips

Structure of QR Codes

QR code (Quick response code) is a matrix 2D code for high-speed reading developed by DENSO WAVE in 1994. It was registered to the ITS standard of the AIMI in 1997 and to ISO/IEC standards in 2000.In addition, Micro QR code was standardized as JIS-X-0510 in 2004.

The one guide you need to learn all about 2D codes! This guide provides an easy-to-understand explanation of the structures and standards of 2D codes such as QR code, DataMatrix, and PDF417. Download

Specifications of QR Codes

The smallest element (black or white square) of the QR code is called “a module”. A QR code is composed of a combination of black and white modules, position detection patterns, timing patterns,format information that contains error correction level and mask numbers, data area and error correction code(Reed-Solomon code).

Specifications
Smallest symbol size	21 x 21 modules
Largest symbol size	177 x 177 modules
Maximum data capacity	Numeric	7089 characters
	Alphanumeric	4296 characters
	Kanji	1817 characters

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Position detection patterns

The position detection patterns are arranged at three corners of the QR codes. (Micro QR has one.) The position of QR code is detected with the position detection patterns that allow high-speed reading.From any position of A, B and C, the rate of black and white modules is 1:1:3:1:1 to specify the rotation angle/ displacement of the code.It can be read from any direction, which significantly improves work efficiency.

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Alignment pattern

The alignment pattern is used for position detection when there is displacement of modules due to distortion.It is applied to model 2.

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Margin

The margin is a blank area around the QR code. Model 1 and 2 require a margin of four modules and Micro QR code requires of two modules.

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Timing pattern

White and black modules are alternately arranged to determine the coordinate.

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Format information

It contains the error correction rate and mask pattern of the code. The format information is read first when the code is decoded.

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Error-correcting code (Reed-Solomon code)

Reed-Solomon code is applied to restore the data when a part of QR code is missing or damaged. The restoration rate varies on 4 different error correcting levels.

Error correcting level	Damaged area to entire code size
L	7%
M	15%
Q	25%
H	30%

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Arrangement of error-correcting code

Data and error correcting code are arranged as shown below. (Sample: Version 2 of Model 2 with level M) A mask is applied to the code to prevent the same pattern with the position detection pattern from appearing.

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