ISO/IEC 21471:2025

International
Standard
ISO/IEC 21471
Second edition
Information technology —
2025-04
Automatic identification and data
capture techniques — Data Matrix
Rectangular Extension (DMRE) bar
code symbology specification
Reference number
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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© ISO/IEC 2025 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Symbol description. 2
5.1 Basic characteristics .2
5.2 Summary of additional features .3
5.3 Symbol structure .3
5.3.1 General .3
5.3.2 Finder pattern .3
5.3.3 Symbol sizes and capacities .3
6 DMRE requirements . 4
6.1 Encoding procedure overview .4
6.1.1 General .4
6.1.2 Step 1: Data encodation .4
6.1.3 Step 2: Error checking and correcting codeword generation .4
6.1.4 Step 3: Module placement in matrix .4
6.2 DMRE symbol attributes .4
6.2.1 Symbol sizes and capacity .4
6.2.2 Insertion of alignment patterns into larger symbols .5
6.3 Structured append .5
6.4 Error detection and correction .5
6.5 Symbol construction .5
6.5.1 General .5
6.5.2 Symbol character placement .6
6.5.3 Alignment pattern module placement .6
6.5.4 Finder pattern module placement .6
7 Symbol dimensions . 6
8 Symbol quality . 7
9 Reference decode algorithm for DMRE . 7
10 User guidelines . 7
10.1 Human readable interpretation .7
10.2 Autodiscrimination capability .7
10.3 System considerations .7
11 Transmitted data . 7
Annex A (informative) DMRE alignment patterns . 8
Annex B (normative) Error correction codeword generator polynomials . 9
Annex C (informative) Symbol character placement .12
Annex D (normative) Symbology identifier . 14
Annex E (informative) Encode example .15
Annex F (informative) Autodiscrimination capability .18
Annex G (informative) System considerations . 19
Bibliography .20

© ISO/IEC 2025 – All rights reserved
iii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
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In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 31, Automatic identification and data capture techniques.
This second edition cancels and replaces the first edition (ISO/IEC 21471:2020), which has been technically
revised.
The main changes are as follows: information duplicated from ISO/IEC 16022 has been removed.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.

© ISO/IEC 2025 – All rights reserved
iv
Introduction
Data Matrix Rectangular Extension (DMRE) is a two-dimensional matrix symbology which is made up
of nominally square modules arranged within a perimeter finder pattern. Though primarily shown and
described in this document as a dark symbol on light background, DMRE symbols can also be printed to
appear as light on dark.
This document is an extension of ISO/IEC 16022, to which it adds rectangular formats. Maximum
compatibility is a design goal. This document only describes the required extension. Common properties are
not repeated. It is a goal to combine ISO/IEC 16022 and this document in the future, when DMRE is widely
adopted.
This document is published separately because existing equipment supporting ISO/IEC 16022 will not
recognize DMRE symbols. Only equipment that is enabled and configured to support DMRE will be capable
of printing and scanning the new rectangular formats.
Manufacturers of bar code equipment and users of the technology require publicly available standard
symbology specifications to which they can refer when developing equipment and application standards.
The publication of standardized symbology specifications is designed to achieve this.

© ISO/IEC 2025 – All rights reserved
v
International Standard ISO/IEC 21471:2025(en)
Information technology — Automatic identification and data
capture techniques — Data Matrix Rectangular Extension
(DMRE) bar code symbology specification
1 Scope
This document defines the requirements for the symbology known as Data Matrix Rectangular Extension
(DMRE). This document specifies the DMRE code symbology characteristics, data character encodation,
symbol formats, dimensions and print quality requirements, error correction rules, decoding algorithm, and
user-selectable application parameters.
This document applies to all DMRE code symbols produced by any printing or marking technology.
Original Data Matrix code sizes are not covered by this document but defined in ISO/IEC 16022 using the
same matrix placement, decoding and error correction algorithm.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 15415, Automatic identification and data capture techniques — Bar code symbol print quality test
specification — Two-dimensional symbols
ISO/IEC 16022, Information technology — Automatic identification and data capture techniques — Data Matrix
bar code symbology specification
ISO/IEC 19762, Information technology — Automatic identification and data capture (AIDC) techniques —
Harmonized vocabulary
ISO/IEC 29158, Automatic identification and data capture techniques — Bar code symbol quality test
specification — Direct part mark (DPM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19762 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

© ISO/IEC 2025 – All rights reserved
4 Symbols
e number of erasures
k total number of error correction codewords
n total number of data codewords
N the numerical base in an encodation scheme
p number of codewords reserved for error detection
S symbol character
t number of errors
X horizontal and vertical width of a module
ε error correction codeword
5 Symbol description
5.1 Basic characteristics
DMRE is a two-dimensional matrix symbology. It is an extension of the ISO/IEC 16022 Data Matrix
symbology.
The characteristics of DMRE are:
a) An encodable character set of:
[2]
1) values 0 to 127 according to the ISO/IEC 646 (International Reference Version) IRV, i.e. all 128
ASCII characters;
2) values 128 to 255 according to ISO/IEC 8859-1 (these are referred to as extended ASCII);
3) additional characters can be encoded using the ECI capabilities.
b) Data is represented as a dark module for the binary one and a light module for zero.
This document specifies DMRE symbols in terms of dark modules marked on a light background.
However, 5.2 indicates that symbols may also be produced with the module’s colours reversed. In such
symbols, dark modules would be a binary zero and light modules would be a binary one.
c) The symbol size in modules (not including quiet zone) are: 8 × 48 to 26 × 64 even values only (see
Table 1).
Symbol sizes 8 × 18, 8 × 32, 12 × 26, 12 × 36, 16 × 36 and 16 × 48 are defined by ISO/IEC 16022 and
are not covered by this document. These rectangular Data Matrix sizes are fully compatible with this
document.
NOTE Only the symbol's size characteristic is different from the ISO/IEC 16022 Data Matrix symbology.
d) Data characters per symbol (for maximum symbol size) are as follows:
1) alphanumeric data: up to 175 characters;
2) 8-bit byte data: 116 characters;
3) numeric data: 236 digits.
e) The code type is rectangular matrix.

© ISO/IEC 2025 – All rights reserved
f) The orientation is independent.
g) The error detection and correction is Reed Solomon.
5.2 Summary of additional features
Additional features which are inherent or optional in DMRE are:
a) Reflectance reversal (inherent): Symbols are either dark on light or light on dark (see Figure 1). The
specifications in this document are based on dark images on a light background, therefore references to
dark or light modules should be taken as references to light or dark modules respectively in the case of
symbols produced with reflectance reversal.
b) Extended channel interpretations (ECI) (inherent): This mechanism enables characters from other
character sets (e.g. Arabic, Cyrillic, Greek, Hebrew) and other data interpretations or industry-specific
requirements to be represented.
c) Structured append (optional): This allows files of data to be represented in up to 16 Data Matrix
Rectangular Extension symbols. The original data can be correctly reconstructed regardless of the order
in which the symbols are scanned. If the feature is not implemented, data should not be transmitted in
case of a structured append symbol.
NOTE All the additional features in this subclause are identical to ISO/IEC 16022 Data Matrix symbology.
5.3 Symbol structure
5.3.1 General
Each DMRE symbol consists of data regions which contain nominally square modules set out in a regular
array. In larger symbols, data regions are separated by alignment patterns. The data region is surrounded
by a finder pattern, and this shall be surrounded on all four sides by a quiet zone border. Figure 1 illustrates
two representations of a Data Matrix Rectangular Extension symbol, dark on light and reflectance reversal.
a) DMRE, dark on light b) DMRE, light on dark (reflectance reversal)
Figure 1 — DMRE “A1B2C3D4E5F6G7H8I9J0K1L2”
5.3.2 Finder pattern
The finder pattern is a perimeter to the data region and is one module wide. Two adjacent sides, the left
and lower sides, forming the L boundary, are solid dark lines; these are used primarily to determine
physical size, orientation and symbol distortion. The two opposite sides are made up of alternating dark
and light modules. These are used primarily to define the cell structure of the symbol, but also can assist
in determining physical size and distortion. The extent of the quiet zone is indicated by the corner marks in
Figure 1.
5.3.3 Symbol sizes and capacities
DMRE symbols have an even number of rows and an even number of columns. The symbols are rectangular
with sizes from 8 × 48 to 26 × 64 not including quiet zones. For all Data Matrix Rectangular Extension
symbols, the upper right corner module has the opposite reflectance state (i.e. light or dark) of the “L” finder
pattern (see Figure 1). The complete attributes are given in Table 1.

© ISO/IEC 2025 – All rights reserved
6 DMRE requirements
6.1 Encoding procedure overview
6.1.1 General
This subclause provides an overview of the encoding procedure. Subclauses 6.1.2 to 6.1.4 provide more
details. An encoding example for DMRE is given in Annex E. The following steps given in 6.1.2 to 6.1.4 convert
user data to a DMRE symbol.
6.1.2 Step 1: Data encodation
As DMRE includes various encodation schemes that allow a defined set of characters to be converted into
codewords more efficiently than the default scheme, analyse the data stream to identify the variety of
different characters to be encoded. Insert additional codewords to switch between the encodation schemes
and to perform other functions. Add pad characters as needed to fill the required number of codewords.
If the user does not specify the matrix size, then choose the smallest size that accommodates the data. A
complete list of matrix sizes is shown in Table 1.
Refer to ISO/IEC 16022 Data Matrix for a description of this step.
6.1.3 Step 2: Error checking and correcting codeword generation
Generate the error correction codewords for the data codeword stream from above step. The result of
this process expands the codeword stream by the number of error correction codewords. Place the error
correction codewords after the data codewords.
6.1.4 Step 3: Module placement in matrix
Place the codeword modules in the matrix. Insert the alignment pattern modules, if any, in the matrix. Add
the finder pattern modules around the matrix.
6.2 DMRE symbol attributes
6.2.1 Symbol sizes and capacity
There are 18 rectangular symbols available in DMRE. These are as specified in Table 1.

© ISO/IEC 2025 – All rights reserved
Table 1 — DMRE symbol attributes
Symbol Total Reed-Solomon Max.
Data region Map- Max. data capacity % of code-
a
size codewords block Inter– correctable
ping words used
leaved codewords
matrix for error
blocks Error/
b
Row Col. Size No. Data Error Data E
...