Frontend Accessibility

Applies to components in <ui-packages-dir> and pages in <web-dir>/src/. The target is WCAG 2.1 Level AA, and it is a floor rather than a goal.

Resolving project conventions

Values in angle brackets come from the project's stack profile. Resolve them in this order:

Read STACK-PROFILE.md at the repo root and use its values verbatim.
If it is absent or a key is missing, infer from the repo — css-strategy and ui-framework from the web application's dependencies.
If still unresolved, match the dominant convention already present in the repo.
Only when the repo is empty, fall back to this skill's stated default — then write the chosen values into STACK-PROFILE.md.

Never invent a new convention when the repo already expresses one.

Hard rules

1. Semantic HTML first

<button> for actions, <a> for navigation. Never a <div> with a click handler.
Heading levels descend without skipping.
<label> for every form field, associated with htmlFor.
<fieldset> and <legend> for grouped controls.
Landmarks — <nav>, <main>, <footer>, <aside> — on every page.

2. ARIA only where HTML cannot

The order of preference is semantic element, then ARIA attribute, then custom behavior. Never use ARIA to override semantics an element already carries — a role="button" on a <div> reimplements, badly, what <button> gives free.

Incorrect ARIA is worse than none: a wrong aria-label silently replaces the accessible name a screen reader would otherwise compute correctly.

3. Keyboard operation is mandatory

Everything interactive is reachable with Tab.
Tab order follows visual order.
Focus is always visible. Never remove an outline without replacing it.
Escape closes dialogs and popovers; Enter and Space activate controls; arrow keys move within composite widgets.
Custom widgets manage focus explicitly.

4. Color and contrast

4.5:1 for normal text, 3:1 for large text (18px, or 14px bold) and for meaningful UI boundaries.
Color never carries meaning alone — pair it with text, an icon, or a pattern.
Both themes are checked, not just the default one.

5. Images and media

Every image has alt. Descriptive for content, alt="" for decoration.
Never "image", "photo", or the filename.
Complex images get a long description through aria-describedby or a caption.
Video carries captions; audio carries a transcript.

6. Forms

Every input labelled.
Errors linked with aria-describedby and announced with role="alert".
Invalid fields marked aria-invalid.
Required fields marked with the required attribute — and if an asterisk is shown, its meaning is stated in text somewhere.
On a failed submit, focus moves to the first invalid field.

7. Target size

WCAG 2.1 AA has no minimum target size (2.2 AA sets 24×24 CSS px; the 44×44 figure is 2.1 AAA and the platform HIG convention). Treat 44×44 as the floor for primary actions on touch surfaces, and apply it as follows:

Primary and destructive actions, and anything a user reaches for on a phone: 44×44.
Dense desktop chrome — toolbars, table row actions, compact form controls — may go smaller, down to 24×24, provided the targets are not adjacent to other targets and an equivalent full-size control exists elsewhere.
Spacing counts. A 32px control with 6px of clear space on each side meets the 2.2 criterion; a 32px control butted against its neighbour does not.

Vendored component libraries typically ship below this floor — a default button height of 32 or 36 CSS px is common. Do not hand-edit the vendored file to fix it, and do not treat the mismatch as acceptable by default. Raise the default in <wrappers-pkg> so every consumer inherits the compliant size, and keep the smaller sizes available as explicit opt-ins for dense contexts. That way the accessible choice is the one you get by not thinking about it.

Record which resolution the project took in STACK-PROFILE.md. An unstated waiver gets rediscovered as a bug every six months.

8. Motion

Respect prefers-reduced-motion.
Auto-playing content has a pause control.
Nothing flashes more than three times per second.

9. Testing is part of the work

Operate the feature with the keyboard alone.
Listen to it with a screen reader — VoiceOver on macOS, NVDA on Windows.
Run an automated scan in the end-to-end suite.

Automated tools catch roughly a third of real issues. They are a floor, not a pass.

Patterns

Full implementations live in references/component-patterns.md. What each pattern guarantees:

Button — a semantic <button> whose focus ring shows for keyboard users but not mouse clicks (focus-visible), with motion-safe transitions and an ariaLabel prop for icon-only use.
Form input — a labelled input whose error text is programmatically linked with aria-describedby, announced with role="alert", and flagged with aria-invalid; the required asterisk is aria-hidden.
Dialog — a native <dialog> using showModal() for free focus trapping, Escape handling, and inert background; focus moves in on open and restores to the trigger on close.
Listbox — a custom select with roving arrow-key navigation and correct ARIA wiring (aria-activedescendant, role="listbox"); build it only when a native <select> does not fit.
Skip link — lets keyboard users jump past the navigation, visible only when focused; the target carries tabIndex={-1} so focus actually lands there.

WCAG quick reference

Principle	Requirement	In practice
Perceivable	Content available to every sense	Alt text, captions, colour plus icon
Operable	Everything reachable by keyboard	Tab order, Escape closes, focus visible
Understandable	Predictable, clearly worded	Consistent navigation, plain language
Robust	Works with assistive technology	Valid HTML, correct ARIA, semantic elements

Issue	Fix
Unlabelled input	Add `<label htmlFor>`
Low contrast	Meet 4.5:1, or 3:1 for large text
No keyboard path	Real interactive elements, managed focus
Missing alt	Describe it, or `alt=""` if decorative
Colour-only meaning	Add text or an icon
Icon-only button	Add `aria-label`
Flashing content	Keep under three flashes per second

Motion preferences

Handle reduced motion in plain CSS. A utility-class variant such as motion-safe: only applies when motion is allowed, so putting it inside a reduced-motion query produces a rule that can never match.

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

Near-zero rather than none keeps transition-end events firing, so components waiting on them do not hang.

For per-component control, apply the motion-safe: variant to the animated utility itself — motion-safe:transition-colors, as in the Button above.

Visually hidden content

Most utility frameworks already ship sr-only and not-sr-only. Use them; do not redefine them. If yours does not, the reference implementation lives in references/component-patterns.md.

Testing checklist

Keyboard

Every interactive element reachable by Tab
Tab order matches visual order
Focus always visible
Escape closes dialogs and popovers
Arrow keys work in composite widgets
Focus returns to the trigger when a dialog closes

Screen reader

All content reachable
Control purposes clear without surrounding context
Labels announced with their fields
Errors announced through role="alert"
Landmarks present
Decorative elements hidden with aria-hidden

Colour

4.5:1 normal text, 3:1 large text and UI boundaries
No colour-only meaning
Both themes verified

Motion

Reduced-motion honoured
No flashing beyond three per second
Auto-playing content pausable

Automated

Scans run inside the Playwright suite — see frontend-testing. The Axe-in-Playwright snippet lives in references/component-patterns.md.

Reference documents

Deep dive	Reference
Accessible component implementations: button, form input, modal, listbox, skip link	`references/component-patterns.md`

Related skills

frontend-architecture — component layering and theming
frontend-testing — where these checks run
frontend-component-docs — documenting a component's accessibility contract

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