Purpose
Accessibility engineering ensures that digital products are usable by people with disabilities. This handbook provides the principles, standards and practices for building accessible software.
Accessibility is not a feature — it is a fundamental quality attribute of well-engineered software.
Scope
This handbook covers:
- Accessibility principles and philosophy.
- Standards and compliance (WCAG, ARIA, Section 508).
- Inclusive design practices.
- Testing methodology and tooling.
- Integration into development workflows.
- AI-assisted accessibility workflows.
It does not cover:
- Legal or regulatory compliance advice (consult legal counsel).
- Specific assistive technology training.
Principles
Accessibility is a Quality Attribute
Accessibility is not separate from quality — it is a dimension of quality alongside security, performance and maintainability. Accessible software is typically better engineered software for all users.
Inclusive by Default
Design and build for diverse users from the start. Retrofitting accessibility is more expensive and produces worse outcomes than building inclusively from the beginning.
Standards Are the Floor, Not the Ceiling
WCAG compliance is the minimum standard. Truly accessible products go beyond compliance to deliver excellent experiences for all users.
Automation Augments, Not Replaces, Human Testing
Automated accessibility checks catch ~30% of issues. Manual testing with assistive technologies and human judgement is essential.
Accessibility is Everyone's Responsibility
Engineers, designers, product managers and QA all contribute to accessibility. The engineering handbook focuses on the technical aspects, but accessibility success requires organisational commitment.
Standards
WCAG (Web Content Accessibility Guidelines)
WCAG is the primary international standard for web accessibility. It is organised around four principles (POUR):
| Principle | Description |
|---|---|
| Perceivable | Users must be able to perceive the content. |
| Operable | Users must be able to operate the interface. |
| Understandable | Users must be able to understand the content. |
| Robust | Content must work with current and future tools. |
WCAG has three conformance levels:
| Level | Description |
|---|---|
| A | Minimum level — essential accessibility support. |
| AA | Recommended level — removes common barriers. |
| AAA | Highest level — may not be achievable for all content. |
Target WCAG 2.2 AA as the minimum compliance level.
ARIA (Accessible Rich Internet Applications)
ARIA provides attributes that enhance the accessibility of dynamic content and custom widgets. Follow the Accessibility References for ARIA usage guidelines.
Testing Methodology
| Method | Coverage | When |
|---|---|---|
| Automated checks | ~30% | CI pipeline, every commit. |
| Manual keyboard testing | ~50% | Every feature before merge. |
| Screen reader testing | ~80% | Before release, major features. |
| User testing | ~90%+ | Periodic, with diverse users. |
Integration into Development
Design Phase
- Accessibility requirements in user stories.
- Design reviews include accessibility checklist.
- Colour contrast verified early.
Development Phase
- Use semantic HTML by default.
- Follow ARIA authoring practices.
- Keyboard accessibility tested continuously.
- Accessibility linting in IDE.
Review Phase
- Accessibility checklist in PR review.
- Automated checks in CI pipeline.
- Manual keyboard and screen reader testing.
Release Phase
- Full accessibility audit before major releases.
- QA includes accessibility test cases.
- Regression testing for accessibility.
AI Integration
AI can assist with accessibility engineering:
- Automated accessibility auditing (detecting missing alt text, poor contrast, missing labels).
- Generating accessible code patterns (semantic HTML, ARIA attributes).
- Analysing colour contrast and suggesting alternatives.
- Reviewing forms for accessible error handling.
- Generating alternative text suggestions.
- Identifying focus management issues.
See AI Workflows for Accessibility for prompt patterns.
Capability Map
All documents in the Accessibility Engineering capability:
| Document Type | Document |
|---|---|
| Handbook | Accessibility Engineering Handbook |
| Glossary | Accessibility Glossary |
| Guides | Accessibility Guides |
| Playbooks | Accessibility Review Playbook |
| Checklists | Accessibility Checklists |
| Templates | Accessibility Templates |
| Learning Paths | Accessibility Learning Paths |
| References | Accessibility References |
| AI Workflows | AI Workflows for Accessibility |