What is a QR code?

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 standardised as JIS-X-0510 in 2004.

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.

(1) Position detection patterns
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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.

Alignment pattern
A
Alignment pattern
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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.

Margin
A
Margin
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Timing pattern

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

Timing pattern
A
Timing pattern
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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.

Format information
A
Format information
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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.

Spot
Spot
Stain
Stain
Data missing
Data missing
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.

Arrangement of error-correcting code
A
Data (D1-)
B
Error correcting code (E1-)
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Specifications of QR Codes

QR codes are classified into Model 1, Model 2 and Micro QR. They have different features and data capacities.
“Version” indicates the size (number of modules) of a QR code. A larger version contains greater data. (The actual size of the code increases as well.)
The standard version is 21 x 21 modules (MicroQR has 11 x 11 modules), and as version increases, 4 modules (2 modules for MicroQR) are added on each side.

Model 1

Model 1

Model 1 is the prototype of Model 2 and Micro QR. 1 to 14 versions are registered to the AIMI standard.

Maximum data capacity
Numeric 1167 characters
Alphanumeric 707 characters
Binary 468 bytes
Kanji 299 characters

When a version increases, 4 modules are added to the code in both the X and Y directions.

Model 2

A
Alignment pattern

Model 2 has an alignment pattern for better position adjustment and contains greater data than Model 1. 1 to 40 versions are registered to the AIMI standard. The version 40 can contain up to 7089 numeric characters.

Maximum data capacity
Numeric 7089 characters
Alphanumeric 4296 characters
Binary 2953 bytes
Kanji 1817 characters

When a version increases, 4 modules are added to the code in both the X and Y directions.

A
Data increase
B
Version 1
C
Version 2

Micro QR

Micro QR has only one position detection pattern to reduce the size so that it can be printed on minute components such as printed circuit boards. The least numbers of modules are 11 x 11.
Micro QR codes offer a space-saving alternative to linear barcodes for applications where 35 characters or less are acceptable.

A
Data increase
B
Version 1
C
Version 2
Maximum data capacity
Numeric 35 characters
Alphanumeric 21 characters
Binary 15 bytes
Kanji 9 characters

When a version increases, 2 modules are added to the code in both the X and Y directions.

How to determine the QR code size

The size of QR code is determined by the version and the size of a module.

(1) Determine the version

Select a version according to data contents, character type and error correction rate.
See below for maximum number of input characters.

(2) Determine the module size

Determine the module size considering the resolution of the printer, and the performance of the scanner.

(3) The QR code size is determined

The actual size of QR code is determined by multiplying the number of modules by the printable size of module. Add margins to determine the required space for the QR code. Model 1 and 2 require 4 modules and MicroQR requires 2 modules as margin on each side.

When the module size is 0.25 mm,

the sizes of QR code are:
5.25 x 5.25 mm for version 1 (21 x 21)
8.25 x 8.25 mm for version 4 (33 x 33)
required spaces including margins are:
7.25 x 7.25 mm for version 1 (29 x 29)
10.25 x 10.25 mm for version 4 (41 x 41)
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Data capacity of each version

Model 2

Version (module numbers) Numeric Alphanumeric Binary Kanji
L M Q H L M Q H L M Q H L M Q H
1 (21) 41 34 27 17 25 20 16 10 17 14 11 7 10 8 7 4
2 (25) 77 63 48 34 47 38 29 20 32 26 20 14 20 16 12 8
3 (29) 127 101 77 58 77 61 47 35 53 42 32 24 32 26 20 15
4 (33) 187 149 111 82 114 90 67 50 78 62 46 34 48 38 28 21
5 (37) 255 202 144 106 154 122 87 64 106 84 60 44 65 52 37 27
6 (41) 322 255 178 139 195 154 108 84 134 106 74 58 82 65 45 36
7 (45) 370 293 207 154 224 178 125 93 154 122 86 64 95 75 53 39
8 (49) 461 365 259 202 279 221 157 122 192 152 108 84 118 93 66 52
9 (53) 552 432 312 235 335 262 189 143 230 180 130 98 141 111 80 60
10 (57) 652 513 364 288 395 311 221 174 271 213 151 119 167 131 93 74
11 (61) 772 604 427 331 468 366 259 200 321 251 177 137 198 155 109 85
12 (65) 883 691 489 374 535 419 296 227 367 287 203 155 226 177 125 96
13 (69) 1022 796 580 427 619 483 352 259 425 331 241 177 262 204 149 109
14 (73) 1101 871 621 468 667 528 376 283 458 362 258 194 282 223 159 120
15 (77) 1250 991 703 530 758 600 426 321 520 412 292 220 320 254 180 136
16 (81) 1408 1082 775 602 854 656 470 365 586 450 322 250 361 277 198 154
17 (85) 1548 1212 876 674 938 734 531 408 644 504 364 280 397 310 224 173
18 (89) 1725 1346 948 746 1046 816 574 452 718 560 394 310 442 345 243 191
19 (93) 1903 1500 1063 813 1153 909 644 493 792 624 442 338 488 384 272 208
20 (97) 2061 1600 1159 919 1249 970 702 557 858 666 482 382 528 410 297 235
21 (101) 2232 1708 1224 969 1352 1035 742 587 929 711 509 403 572 438 314 248
22 (105) 2409 1872 1358 1056 1460 1134 823 640 1003 779 565 439 618 480 348 270

Micro QR

Version Error correcting Numeric Alphanumeric Binary Kanji
M1 (11) Error detection 5 - - -
M2 (13) L 10 6 - -
M 8 5 - -
M3 (15) L 23 14 9 6
M 18 11 7 4
M4 (17) L 35 21 15 9
M 30 18 13 8
Q 21 13 9 5
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