ISO/IEC 29138-4:2026

International
Standard
ISO/IEC 29138-4
First edition
Information technology — User
2026-06
interface accessibility —
Part 4:
Applying user accessibility needs
Technologies de l'information — Accessibilité de l'interface
utilisateur —
Partie 4: Prise en compte des besoins d'accessibilité des
utilisateurs
Reference number
© ISO/IEC 2026
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© ISO/IEC 2026 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Conventions . 2
5 User accessibility needs . 2
6 Applying user accessibility needs in development and maintenance . 2
7 Understanding the context of use . 3
8 Contextualizing user accessibility needs . 4
9 Transforming user accessibility needs into user accessibility requirements. 5
10 Ensuring user accessibility requirements are met . 7
10.1 Evaluating an ICT system.7
10.2 Evaluating the meeting of UAR in design, development and maintenance .7
10.3 Evaluating the meeting of UAR in evaluation of ICT systems .8
10.4 Evaluating the meeting of UAN in evaluation of ICT systems .8
11 Applying user accessibility needs in procurement . 8
12 Additional user needs . . 9
Annex A (informative) List of the user accessibility needs from ISO/IEC 29138-1:2018 .10
Bibliography .15

© ISO/IEC 2026 – 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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ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
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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 documents 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).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
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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 35, User interfaces.
A list of all parts in the ISO/IEC 29138 series can be found on the ISO and IEC websites.
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 2026 – All rights reserved
iv
Introduction
The user accessibility needs (UANs) in ISO/IEC 29138-1 provide the most comprehensive set of standardized
user accessibility needs currently available. It is recognized that further UANs are likely to be identified and
that ISO/IEC 29138-1 will be updated over time to incorporate these further UANs. The benefit of the set
of UANs in ISO 29138-1 is that they provide a fixed set of issues that are needed to provide accessibility to
diverse users in diverse contexts.
UANs can be applied to the procurement, development, maintenance and evaluation of ICT systems in order
to improve their usability for diverse users in diverse contexts. This document provides guidance on how to
perform this application. It also allows for the application of any further user accessibility needs beyond the
current set found in ISO/IEC 29138-1.

© ISO/IEC 2026 – All rights reserved
v
International Standard ISO/IEC 29138-4:2026(en)
Information technology — User interface accessibility —
Part 4:
Applying user accessibility needs
1 Scope
This document provides guidance on applying the set of user accessibility needs (UANs) to the procurement,
development and evaluation of ICT products and services. This includes guidance on documenting the
application of user accessibility needs.
Applying user accessibility needs helps improve accessibility for all users and in particular for users with
special needs that might otherwise be overlooked.
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 29138-1, Information technology — User interface accessibility — Part 1: User accessibility needs
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
user accessibility need
UAN
user need related to features or attributes that are necessary for a system to be accessible to some users
Note 1 to entry: User accessibility needs vary over time and across contexts of use.
Note 2 to entry: User accessibility needs are transformed into user accessibility requirements considering the context
of use, user priorities, trade-offs with other system requirements and constraints.
[SOURCE: ISO/IEC 29138-1:2018, 3.10, modified —"to some user" has been added to the definition and “user
requirements” in Note 2 to entry has been replaced by “user accessibility requirements”.]
3.2
user accessibility requirement
UAR
use-related quality requirement that supports one or more user accessibility need

© ISO/IEC 2026 – All rights reserved
3.3
context of use
combination of users, goals and tasks, resources and environment
Note 1 to entry: The “environment” in a context of use includes the technical, physical, social, cultural and
organizational environments.
[SOURCE: ISO 9241-11:2018, 3.1.15]
3.4
situation
unique combinations of interrelated users, groups, tasks, resources, and environments within a context of
use
Note 1 to entry: Interrelationships within situations are the primary source of information for identifying user needs
and deriving user requirements for the interactive system.
4 Conventions
The latest version of the user accessibility needs can be obtained from ISO/IEC 29138-1 at https:// www .iso
.org/ standard/ 71953 .html.
NOTE Annex A contains a listing of the user accessibility needs in ISO/IEC 29138-1:2018.
5 User accessibility needs
There is an infinite combination of user characteristics, capabilities and disabilities that can lead to an
infinite set of possible solutions. The diversity of contexts of use further complicates the number of possible
solutions.
ISO/IEC 29138-1 is based on the recognition that these solutions satisfy various combinations of a finite
set of identifiable UANs. It contains the most comprehensive set of user accessibility needs for ICT that
are currently available. However, the user accessibility needs and instances of needs that it contains are
specified in a generic manner that can apply to any ICT system or service.
6 Applying user accessibility needs in development and maintenance
ISO/IEC 30071-1 describes the following activities in ICT system development or procurement:
— Activity 1: Specify the widest range of potential users;
— Activity 2: Specify user goals and tasks (and context of use);
— Activity 3: Specify user accessibility needs;
— Activity 4: Specify accessibility requirements.
— Activity 5: Specify accessibility design approach;
— Activity 6: Ensure accessibility requirements are met;
— Activity 7: Ensure communication about accessibility;
— Activity 8: Ensure integration of accessibility in system updates.
In addition to activity 3, which explicitly identifies specific user accessibility needs, applying user
accessibility needs also involves activities 2, 4, and 6.
— Applying UANs to a particular ICT system requires an understanding of the context of use of the ICT
system, which is part of activity 2. Clause 7 provides guidance on this activity.

© ISO/IEC 2026 – All rights reserved
— Applying UANs to an ICT system or service involves customizing them by contextualizing each specific
UAN to the intended context of use, within activity 3. Clause 8 provides guidance on this activity.
— Incorporating accessibility into the development of an ICT system involves transforming each of the
UANs into user accessibility requirements, within activity 4. Clause 9 provides guidance on this activity.
— Ensuring that accessibility is achieved by an ICT system involves ensuring that the accessibility
requirements, based on UANs, are met, within activity 6. Clause 10 provides guidance on this activity.
7 Understanding the context of use
Activity 2 of ISO/IEC 30071-1 focuses on specifying the user goals and tasks within the context of use for a
particular ICT system.
The context of use shall be identified as part of applying UAN to the development or evaluation of ICT
systems.
ISO 9241-11 identifies that the context of use is composed of:
— users
— goals and tasks
— resources
— environments
According to ISO 9241-11:
— Users can be treated as members of user groups which are most appropriately composed of diverse users
with common roles for using with an interactive system. This recognizes that there can be a diversity
of characteristics and capabilities within each user group. It is important to recognize that users from
different groups might both interact with the interactive system and with other users from the same or
other user groups.
— Goals are the intended outcome(s) to be achieved, independent of the means used to achieve them. Goals
focus on what is to be achieved without necessarily specifying criteria (such as levels of effectiveness,
efficiency or satisfaction). Tasks consist of one or more activities undertaken to achieve a goal. Different
combinations of activities can provide different ways of achieving the same goal and can lead to different
levels of usability.
— Resources include any reusable resources and any expendable or exhaustible resources that need to
be used to achieve specified goals. Reusable resources include equipment, applications, information
and support that are used in conjunction with the object of interest while the user is carrying out the
task and that are integral to its completion. Expendable resources include available time, human effort,
financial resources and materials.
— There are a number of identifiable environments in context of use including the technical, physical and
social, cultural and organizational environments that influence usability.
— The technical environment consists of those environmental components that enable or constrain
the use of the reusable and expendable resources. The technical environment typically includes
access to resources such as furniture, packages, control devices, energy (e.g. electrical, chemical or
mechanical) and connectivity (e.g. Internet, cell network).
— The physical environment can include the built environment; spatial, thermal, acoustic and visual
conditions, stability and vibration; geographical and topographical features; weather conditions,
and time of day, and season, depending on which of these has an effect on the use of the system.
— The social, cultural and organizational environment includes other people (including stakeholders);
the roles and relationships between people; organizational structures; language; legislation; norms
and values, and work practices; use in isolation or as part of a group; and privacy.

© ISO/IEC 2026 – All rights reserved
NOTE 1 Further information on users (user groups), goals, tasks, resources, and environments is contained in
ISO 9241-11.
A description of the context of use should be documented in a manner that supports the referencing of
individual situations within the context of use in the development or evaluation of ICT systems.
NOTE 2 ISO 25063identifies items of information to be used in a context of use description.
ISO/IEC Guide 71 recognizes that within the overall context of use (as defined in ISO 9241-11) there exist
many possible individual contexts and that accessible design is focused on diverse users to maximize the
number of potential users who can readily use a system in diverse contexts.
8 Contextualizing user accessibility needs
Activity 3 of ISO/IEC 30071-1 focuses on specifying user accessibility needs for the particular ICT system.
Each need presented in ISO/IEC 29138-1 identifies something that is generally needed by some users to
achieve accessibility, without identifying qualifications on the need, such as: where it is needed or how
the achievement of this need can be verified. UANs can inform but are not intended to be directly used as
requirements.
While most UANs apply to the development or evaluation of ICT systems, it is important to contextualize the
set of UANs in order to most effectively apply them.
Contextualizing a UAN involves inserting specific information from the context of use to adapt it into a
contextualized UAN, substituting it for existing information where appropriate. This specific information
can be direct from the context of use description or more specific information that is obtained from
individual situations within the context of use.
NOTE 1 The various instances of each of the UANs in ISO/IEC 29138-1 are more specific than the general UAN to
which they apply. Each of these instances provides an example of a possible contextualization of the UAN.
Depending on the context of use:
— some UANs apply directly to the interactive system under consideration;
NOTE 2 There are few UANs that cannot benefit from being adapted to better apply to the interactive system
under consideration.
— some UANs can be adapted to better apply to the interactive system under consideration;
EXAMPLE 1 Given an understanding of the context of use where images are expected to be used,
ISO/IEC 29138-1:2018, UAN 6-2-4, “To have text alternatives be provided for all non-textual information”,
can be contextualized to “To have text alternatives for images”. If moving images are also expected, a second
contextualization could be “to have audio descriptions rendered in textual form for dynamic visual content”.
— some UANs can lead to more than one contextualization where different situations lead to different
adaptations of the original UAN;
EXAMPLE 2 ISO/IEC 29138-1:2018, UAN 5-1-1, “to have information presented visually”, is adapted to deal
with situations of very bright lighting (that would be likely to cause glare), typical room lighting and dark
environments.
— some UANs are not applicable to the interactive system under consideration.
EXAMPLE 3 Developers of a software application cannot guarantee that the environment in which their
software is used meets ISO/IEC 29138-1:2018, UAN 4.8, “To have the system free from environmental barriers”.
The UANs of ISO/IEC 29138-1 shall be contextualized as part of applying UANs to the development or
evaluation of ICT systems.
Where additional UANs are identified, they should be added to the set from ISO/IEC 29138-1 and
contextualized similarly (see also Clause 12).

© ISO/IEC 2026 – All rights reserved
While many UANs (e.g. UAN 5.1.1, “To have information presented visually”, and UAN 5.1.2, “To have visual
information available in other modalities”) appear to be fundamental across ICT systems, the context of use
can preclude their applicability (e.g. users will not want to take their visual attention off driving a vehicle in
order to look at a visual display). They might also be inappropriate for a context involving purely auditory
content or devices unable to deliver visual output.
A finding that a UAN is directly applicable without adapting for a context shall be justified by identifying
why it applies to all contexts of use, or why no contextualization is required for that context.
A finding that a UAN is “not applicable” shall be justified according to the context of use and is not made just
to avoid difficult requirements on an ICT system.
A finding that a UAN is to be adapted shall be justified via reference to the component(s) of the context of use
that inform the adaptation.
The contextualization of UANs shall be reported in the development or evaluation of ICT systems.
A report on the contextualization of UANs shall include for each UAN:
a) a unique identifier for the UAN (e.g. the user need number from ISO/IEC 29138-1);
b) the wording of the initial UAN (e.g. the name of the need from ISO/IEC 29138-1);
c) an evaluation of how the UAN has been contextualized (directly used, adapted, or not applicable): Where
a UAN is not applicable in a context, this shall be justified with reference to the capabilities of the system
in development or maintenance and the context of use under consideration;
d) the reasoning for the contextualization;
e) (for adapted UANs) the new wording of the contextualized UAN.
9 Transforming user accessibility needs into user accessibility requirements
Activity 4 of ISO/IEC 30071-1 focuses on transforming user accessibility needs into user accessibility
requirements for the particular ICT system.
Developers and evaluators focus on applying requirements rather than statements of needs. Thus,
...