Use this skill when implementing web accessibility, adding ARIA attributes, ensuring keyboard navigation, or auditing WCAG compliance. Triggers on accessibility, a11y, ARIA roles, screen readers, keyboard navigation, focus management, color contrast, alt text, semantic HTML, and any task requiring WCAG 2.2 compliance or inclusive design.
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Use this skill when implementing web accessibility, adding ARIA attributes, ensuring keyboard navigation, or auditing WCAG compliance. Triggers on accessibility, a11y, ARIA roles, screen readers, keyboard navigation, focus management, color contrast, alt text, semantic HTML, and any task requiring WCAG 2.2 compliance or inclusive design.
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Accessibility & WCAG
A production-grade skill for building inclusive web experiences. It encodes
WCAG 2.2 standards, ARIA authoring practices, keyboard interaction patterns,
and screen reader testing guidance into actionable rules and working code.
Accessibility is not a checkbox - it is the baseline quality bar. Every user
deserves a working product, regardless of how they interact with it.
When to use this skill
Trigger this skill when the user:
Asks to make a component or page accessible or "a11y compliant"
Needs to add ARIA roles, states, or properties to custom widgets
Wants keyboard navigation implemented for interactive components
Asks about screen reader support, announcements, or live regions
Needs a WCAG 2.2 audit or compliance review
Is working on focus management (modals, SPAs, route changes)
Asks about color contrast, alt text, semantic HTML, or form labeling
Is building custom widgets (dialog, tabs, combobox, menu, tooltip)
Do NOT trigger this skill for:
Pure backend code with no HTML output or DOM interaction
CSS-only styling questions that have no accessibility implications
Key principles
Semantic HTML first - The single highest-leverage accessibility action is using the right HTML element. <button> gives you keyboard support, focus, activation, and screen reader announcement for free. No ARIA patch matches it.
ARIA is a last resort - ARIA fills gaps where native HTML falls short. Before adding an ARIA attribute, ask: "is there a native element that does this?" If yes, use that element instead. Bad ARIA is worse than no ARIA.
Keyboard accessible everything - If a sighted mouse user can do something, a keyboard-only user must be able to do the same thing. There are no exceptions in WCAG 2.1 AA. Test every interaction without a mouse.
Test with real assistive technology - Automated tools catch approximately 30% of WCAG failures. The remaining 70% - focus management correctness, announcement quality, logical reading order, cognitive load - requires manual testing with VoiceOver, NVDA, or real users with disabilities.
Accessibility is not optional - It is a legal requirement (ADA, Section 508, EN 301 549), a quality signal, and the right thing to do. Build it in from the start; retrofitting is ten times harder than doing it correctly the first time.
Core concepts
POUR Principles (WCAG foundation)
Every WCAG criterion maps to one of four properties:
Principle
Definition
Examples
Perceivable
Info must be presentable to users in ways they can perceive
Alt text, captions, sufficient contrast, adaptable layout
Operable
UI must be operable by all users
Keyboard access, no seizure-triggering content, enough time
All interactive ARIA controls must be keyboard operable
Don't apply aria-hidden="true" to focusable elements
All interactive elements must have an accessible name
Focus Management Model
Tab order follows DOM order - keep DOM order logical and matching visual order
tabindex="0" - adds element to natural tab order
tabindex="-1" - programmatically focusable but removed from tab sequence
tabindex="1+" - avoid; creates unpredictable tab order
Roving tabindex - composite widgets (tabs, toolbars, radio groups): only one item in tab order at a time; arrow keys navigate within
Focus trap - modal dialogs must trap Tab/Shift+Tab within the dialog
Focus return - always return focus to the trigger element when a modal or overlay closes
Common tasks
1. Write semantic HTML for common patterns
Choose elements for meaning, not appearance. Native semantics are free accessibility.
<!-- Page structure --><header><navaria-label="Primary navigation"><ul><li><ahref="/">Home</a></li><li><ahref="/about">About</a></li></ul></nav></header><mainid="main-content"tabindex="-1"><h1>Page Title</h1><article><h2>Article heading</h2><p>Content...</p></article><asidearia-label="Related links">...</aside></main><footer><navaria-label="Footer navigation">...</nav></footer><!-- Skip link - must be first focusable element --><ahref="#main-content"class="skip-link">Skip to main content</a>
For detailed accessible Dialog (Modal) and Tabs implementations with focus trapping, roving tabindex, and correct ARIA roles/states, see references/widget-examples.md.
4. Ensure color contrast compliance
WCAG AA contrast requirements:
Element
Minimum ratio
Normal text (< 18pt / < 14pt bold)
4.5:1
Large text (>= 18pt / >= 14pt bold)
3:1
UI components (input borders, icons)
3:1
Focus indicators
3:1 against adjacent color
/* Focus ring - must meet 3:1 against neighboring colors */:focus-visible {
outline: 3px solid #005fcc;
outline-offset: 2px;
border-radius: 2px;
}
/* Never convey information by color alone */.field-error {
color: #c0392b; /* red - supplementary only */display: flex;
align-items: center;
gap: 0.25rem;
}
/* The icon + text label carry the meaning; color is an enhancement */.field-error::before {
content: '';
display: inline-block;
width: 1em;
height: 1em;
background: url('error-icon.svg') no-repeat center;
}
<!-- Informative image: describe purpose, not appearance --><imgsrc="revenue-chart.png"alt="Q4 revenue: grew from $2M in October to $3.5M in December"><!-- Decorative image: empty alt, screen reader skips it --><imgsrc="decorative-wave.svg"alt=""><!-- Functional image (inside link or button): describe the action --><ahref="/home"><imgsrc="logo.svg"alt="Acme Corp - Go to homepage"></a><button><imgsrc="search-icon.svg"alt="Search"></button><!-- Complex image: short alt + long description --><figure><imgsrc="architecture-diagram.png"alt="System architecture overview"aria-describedby="arch-desc"><figcaptionid="arch-desc">
The frontend (React) calls an API gateway which routes to three microservices:
auth, products, and orders. All services write to PostgreSQL.
</figcaption></figure><!-- Form labels: explicit association is most robust --><labelfor="email">Email address <spanaria-hidden="true">*</span></label><inputtype="email"id="email"name="email"requiredaria-describedby="email-hint email-error"><spanid="email-hint"class="hint">We'll never share your email.</span><spanid="email-error"role="alert"hidden>
Please enter a valid email address.
</span>
7. Audit accessibility with axe-core and Lighthouse
Tab through every interactive element - reachable? Visible focus? Logical order?
Activate all controls with Enter/Space - do they work without a mouse?
Open every modal/overlay - focus trapped? Escape closes? Focus returns to trigger?
Resize to 400% zoom - content still readable and operable?
Test with VoiceOver (macOS: Cmd+F5) or NVDA (Windows, free) for announcement quality
Load references/aria-patterns.md for complete widget patterns with keyboard interactions.
Anti-patterns
Anti-pattern
Why it fails
Correct approach
<div onclick="..."> as button
No keyboard support, no semantics, not announced as button
Use <button> - it is keyboard focusable, activatable with Space/Enter, and announced correctly
role="button" on a <div>
You still must add tabindex="0", keydown for Enter/Space, and all ARIA states manually
Use <button> - you get all of this for free
aria-hidden="true" on a focused element
Removes element from AT while it has focus - keyboard users are trapped in a void
Never apply aria-hidden to an element that can receive focus
placeholder as the only label
Placeholder disappears on focus, fails contrast requirements, not reliably announced
Always use a visible <label> associated via for/id
tabindex="2" or higher
Creates a parallel tab order separate from DOM order - unpredictable and hard to maintain
Use tabindex="0" (natural order) or tabindex="-1" (programmatic only)
No focus indicator
Keyboard users cannot see where they are on the page; violates WCAG 2.4.7
Use :focus-visible with a high-contrast outline; never outline: none without a visible replacement
Emojis as functional icons
Screen readers announce emoji names inconsistently ("red circle" vs "error"); rendering varies by OS; no contrast or size control
Use SVG icons from Lucide React, Heroicons, Phosphor, or Font Awesome with proper aria-label or aria-hidden
Gotchas
aria-hidden="true" on a focusable element creates a keyboard trap - Screen readers skip the element, but keyboard focus still lands on it. The user is stuck on something invisible. Never apply aria-hidden to any element that can receive focus; remove tabindex or use inert instead.
role="button" without keyboard handlers does nothing - Adding role="button" to a <div> tells screen readers it's a button, but doesn't add keyboard activation. You must also add tabindex="0" and handle both Enter and Space keydown events. Just use <button> instead.
Live regions must be in the DOM before content is injected - aria-live regions only announce changes that happen after they're rendered. If you inject the region and its content at the same time, screen readers won't announce it. Render the empty live region on page load, then populate it.
Focus return after modal close is not automatic - When a modal closes, focus goes to <body> by default. Users lose their place in the page. Always store document.activeElement before opening a modal and call .focus() on that element when the modal closes.
Automated tools catch ~30% of violations - axe and Lighthouse pass does not mean WCAG compliant. Focus order, announcement quality, color-alone information encoding, and logical reading order all require manual testing with a screen reader (VoiceOver on macOS, NVDA on Windows).
References
For detailed patterns and widget specifications, load the relevant reference:
references/aria-patterns.md - Complete ARIA widget patterns: combobox, menu, tree, listbox, accordion, tooltip with correct roles, states, and keyboard interactions
references/widget-examples.md - Accessible Dialog (Modal) and Tabs implementations with focus trapping and roving tabindex
Only load reference files when the current task requires that depth - they contain dense technical detail.
Companion check
On first activation of this skill in a conversation: check which companion skills are installed by running ls ~/.claude/skills/ ~/.agent/skills/ ~/.agents/skills/ .claude/skills/ .agent/skills/ .agents/skills/ 2>/dev/null. Compare the results against the recommended_skills field in this file's frontmatter. For any that are missing, mention them once and offer to install:
