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ISO/IEC 29138-1 — Accessibility — Part 1: User Needs
A comprehensive framework for identifying and documenting the accessibility needs of users with disabilities
Identifying and Documenting User Accessibility Needs
ISO/IEC 29138-1 provides a comprehensive framework for identifying and documenting the accessibility needs of users, serving as a foundational reference for anyone involved in designing, developing, or procuring information technology products and services. Rather than prescribing specific technical solutions, this standard focuses on understanding what users with different disabilities actually need from technology — a critical first step that is often overlooked in favor of jumping directly to compliance checklists and technical standards. The standard was developed through extensive consultation with disability advocacy organizations, accessibility researchers, and most importantly, users with diverse disabilities across multiple countries.
ISO/IEC 29138-1 identifies over 200 distinct user accessibility needs organized across 12 categories, providing the most comprehensive catalog of user-level accessibility requirements in any international standard. This catalog serves as both a design checklist and an evaluation framework throughout the product lifecycle.
The standard was developed by canvassing users with a wide range of disabilities — including vision impairments, hearing loss, mobility limitations, cognitive disabilities, speech impairments, and multiple disabilities — as well as older adults whose functional abilities may change with age. It avoids prescribing implementation technologies, making it technology-neutral and future-proof. Instead, it describes what users need to be able to do, leaving designers and developers to determine how best to meet those needs within their specific product context. This approach ensures that the standard remains relevant as technology evolves — needs described in terms of user outcomes do not become obsolete when new interaction paradigms emerge.
A distinctive feature of ISO/IEC 29138-1 is its explicit recognition that accessibility needs exist on a spectrum rather than as discrete categories. Many users have combinations of accessibility needs, and individual needs vary in intensity across different contexts and over time. The standard encourages designers to consider the full range of human diversity rather than designing for a narrow “typical” user. This perspective is increasingly important as technology becomes embedded in every aspect of daily life, from healthcare to education to employment.
The Twelve Categories of User Needs
Perception, Operation, and Understanding Needs
The standard organizes accessibility needs into twelve categories that span the full spectrum of human-technology interaction. Perception needs cover requirements for receiving information through multiple sensory channels — users who cannot see need auditory or tactile alternatives, while users who cannot hear need visual alternatives. Operation needs address how users control and interact with technology, including alternative input methods, adjustable timing, and error tolerance. Understanding needs cover language, literacy, numeracy, and cognitive support requirements. The categories are designed to be mutually exclusive and collectively exhaustive, ensuring that no significant area of user need is overlooked during the requirements gathering process.
| Category | Number of Needs | Example Needs | Applies To |
|---|---|---|---|
| A — Perception of visual information | 24 | Text alternatives, adjustable font size, high contrast, color independence | All visual outputs |
| B — Perception of auditory information | 18 | Captions, visual indicators, adjustable volume, speech-to-text | All auditory outputs |
| C — Perception of tactile/haptic information | 12 | Braille output, tactile indicators, vibration patterns | Touch-based interfaces |
| D — Operation (no physical contact) | 16 | Speech recognition, eye gaze, gesture control | Hands-free operation |
| E — Operation (with physical contact) | 22 | Keyboard access, switch access, adjustable key repeat, large targets | All physical controls |
| F — Simplicity and cognitive support | 28 | Clear navigation, consistent layout, error prevention, minimal steps | All interfaces |
| G — Accessibility of personal documentation | 14 | Accessible help, plain language summaries, screen reader friendly docs | Documentation |
| H — Accessibility of service support | 16 | Multiple contact methods, relay service support, accessible billing | Customer service |
| I — Accessibility of physical environment | 18 | Adjustable mounting, lighting control, minimal glare, clear floor space | Physical installations |
| J — Safety and emergency information | 14 | Multi-modal emergency alerts, accessible safety instructions | Safety systems |
| K — Privacy and security for accessibility | 10 | Private use of assistive technologies, accessible authentication | All systems |
| L — Compatibility with assistive technologies | 20 | Standard APIs, driver support, input event forwarding | All platforms |
The user needs catalog in ISO/IEC 29138-1 has been adopted as the basis for accessibility requirements in multiple national procurement frameworks, creating a harmonized approach to accessible public sector IT procurement across different countries. This harmonization reduces compliance costs for technology vendors who serve multiple markets.
Privacy and Compatibility Considerations
An often-overlooked category in the standard is privacy and security for accessibility (Category K). Users with disabilities may need to use assistive technologies in public or shared settings, and the design of the system should not force them to disclose their disability. For example, a screen reader user should not be required to remove headphones in a public kiosk setting, and accessible authentication methods (such as biometric alternatives to CAPTCHA) must be provided without compromising security. Category L addresses the critical need for compatibility with assistive technologies through standard platform accessibility APIs, consistent input event models, and support for assistive technology drivers. The standard emphasizes that compatibility should be built into the platform architecture rather than added as an afterthought, as retrofitting accessibility compatibility is typically 5-10 times more expensive than designing it in from the start.
Ignoring accessibility compatibility requirements is one of the most common causes of assistive technology failures. An application that uses non-standard UI frameworks or bypasses platform accessibility APIs will often be completely invisible to screen readers, regardless of how well the visual design follows accessibility guidelines. This is particularly common in applications built with game engines or custom rendering pipelines.
Applying the Standard in Product Development
ISO/IEC 29138-1 is designed to be used at multiple stages of the product lifecycle. During requirements gathering, the user needs catalog serves as a checklist to ensure that the needs of diverse user groups are considered. During design, the need-to-requirement mapping method described in the standard helps translate user needs into measurable design requirements. During evaluation, the same catalog provides criteria for accessibility testing. The standard includes a mapping to several related accessibility standards, including ISO/IEC 29136 (UI accessibility) and ISO 9241-20 (accessibility of ICT products), enabling a cohesive accessibility implementation strategy. This layered approach allows organizations to use ISO/IEC 29138-1 at the strategic level to define their accessibility goals, while ISO/IEC 29136 provides the detailed technical requirements for achieving those goals in user interface design.
For engineering teams, the standard provides practical guidance on integrating user needs identification into existing development processes. The standard recommends including accessibility criteria in user story definitions, conducting accessibility-focused design sprints, and establishing accessibility checkpoints in the development workflow. It also addresses organizational aspects such as training requirements for development teams, the role of accessibility champions within product teams, and the importance of executive sponsorship for accessibility initiatives. The standard recognizes that organizational commitment is as important as technical implementation in achieving meaningful accessibility outcomes.
The most significant risk when using this standard is treating it as a static checklist rather than an iterative discovery process. User needs evolve as technology evolves — needs that were previously unmet may become addressable through new technologies, and new usage contexts may create accessibility challenges that were not previously identified. Regular review and update of user needs is essential. The standard recommends annual review cycles for the user needs catalog within each organization.
Frequently Asked Questions
Q: How does ISO/IEC 29138-1 differ from ISO/IEC 29136?
A: ISO/IEC 29136 focuses on the technical requirements for accessible user interface design. ISO/IEC 29138-1 focuses on the user needs that drive those requirements. The two standards are complementary: 29138-1 defines what users need, and 29136 defines how to implement those needs in UI design. Using both standards together provides a complete accessibility strategy.
A: ISO/IEC 29136 focuses on the technical requirements for accessible user interface design. ISO/IEC 29138-1 focuses on the user needs that drive those requirements. The two standards are complementary: 29138-1 defines what users need, and 29136 defines how to implement those needs in UI design. Using both standards together provides a complete accessibility strategy.
Q: Can this standard be used for web accessibility specifically?
A: Yes. While the standard is technology-neutral, its user needs catalog maps directly to WCAG success criteria. Organizations that use ISO/IEC 29138-1 as a foundation often find that their WCAG compliance efforts are more focused and effective because they understand the underlying user needs that the technical requirements are designed to address.
A: Yes. While the standard is technology-neutral, its user needs catalog maps directly to WCAG success criteria. Organizations that use ISO/IEC 29138-1 as a foundation often find that their WCAG compliance efforts are more focused and effective because they understand the underlying user needs that the technical requirements are designed to address.
Q: What is the recommended approach for involving users with disabilities in the design process?
A: The standard recommends participatory design methods, including co-design workshops, usability testing with assistive technology users, and longitudinal field studies. It emphasizes that user involvement should occur throughout the development cycle, not only at the evaluation stage. The standard provides practical guidance on compensation, accessibility of research activities themselves, and recruitment strategies for reaching diverse disability communities.
A: The standard recommends participatory design methods, including co-design workshops, usability testing with assistive technology users, and longitudinal field studies. It emphasizes that user involvement should occur throughout the development cycle, not only at the evaluation stage. The standard provides practical guidance on compensation, accessibility of research activities themselves, and recruitment strategies for reaching diverse disability communities.
Q: How should organizations prioritize among the 200+ user needs?
A: The standard recommends prioritizing based on the product’s context of use, the target user population, the severity of exclusion if a need is not met, and the feasibility of implementation. A risk-based approach that addresses the most critical exclusions first is strongly advised. The standard provides a prioritization matrix that considers both user impact and implementation complexity.
A: The standard recommends prioritizing based on the product’s context of use, the target user population, the severity of exclusion if a need is not met, and the feasibility of implementation. A risk-based approach that addresses the most critical exclusions first is strongly advised. The standard provides a prioritization matrix that considers both user impact and implementation complexity.
