name: a11y-base-web description: Foundational accessibility patterns and requirements for AI-generated web code. This skill provides baseline rules for semantic HTML, ARIA usage, keyboard navigation, contrast, and inclusive language. Load this skill first before any accessibility analysis, remediation, or validation work. Other a11y skills (web-standards, a11y-remediator, a11y-validator, a11y-tester) build upon these fundamentals.

Accessibility Fundamentals

Baseline accessibility patterns and requirements for technologies that render HTML and CSS.

LLM Behavior and Tone Requirements

In addition to producing accessible code, GitHub Copilot and similar tools must also demonstrate respectful and bias-aware behavior in accessibility contexts. All generated output must follow these principles:

• Respectful, Inclusive Language Use people-first language when referring to disabilities or accessibility needs (e.g., “person using a screen reader,” not “blind user”). Avoid stereotypes or assumptions about ability, cognition, or experience.

• Bias-Aware and Error-Resistant Avoid generating content that reflects implicit bias or outdated patterns. Critically assess accessibility choices and flag uncertain implementations.

• Verification-Oriented Responses When suggesting accessibility implementations or decisions, include reasoning or references to standards (e.g., WCAG, platform guidelines). If uncertainty exists, the assistant should state this clearly.

• Clarity Without Oversimplification Provide concise but accurate explanations—avoid fluff, empty reassurance, or overconfidence when accessibility nuances are present.

• Tone Matters Copilot output must be neutral, helpful, and respectful. Avoid patronizing language, euphemisms, or casual phrasing that downplays the impact of poor accessibility.

Anti-Patterns and Mistakes to Avoid

• Using only placeholders to label inputs
• Suppressing visible focus with CSS resets or browser overrides
• Invalid ARIA usage on elements with semantic roles
• Invalid ARIA: Applying unsupported ARIA states to incorrect elements
• Don’t apply role="button" to a Button <button>

Bad Code example

<button role="button">Click me</button>

Good Code example

<button>Click me</button>

• Don't apply role="link" to a Link <a>

Bad Code example

<a role="link" href="#">Click me</a>

Good Code example

<a href="#">Click me</a>

• Don't apply role="button" to a link <a>

Bad Code example

<a role="button" href="#">Click me</a>      

Good Code example

<a href="#">Click me</a>

• Don't apply role="link" to a Button <button>

Bad Code example

<button role="link">Click me</button>   

Good Code example

<button>Click me</button>

• Don't add aria-label to a button or link unless asked to

Bad Code example

<button aria-label="Click me">Click me</button>

Good Code example

<button>Click me</button>

• Avoid overuse of sectioning elements and ARIA landmarks
• Don't add any ARIA attributes unless asked to, rely on web standards first
• Using generic containers when semantic elements would be more appropriate
• Making entire large areas clickable when a specific element would suffice
• Separating interactive elements from their related content
• Breaking up natural content relationships with unnecessary containers

Semantic Structure Best Practices

Content Organization

When presenting collections of similar items (like articles, cards, products):

1. Prefer list structures (<ul>, <ol>, <li>) over generic containers
2. Place headings within their related content containers, not as wrappers
3. Ensure the natural reading order matches the visual order
4. Keep interactive elements (links, buttons) close to their related content

Content Hierarchy

• Place the most important identifying content first within containers
• Group related content (e.g., image + heading + description) meaningfully
• Avoid unnecessary nesting levels
• Consider the logical order when content will be linearized

Interactive Elements

• Place interactive elements (links, buttons) on the most specific related content
• Avoid making large areas interactive when a smaller target would suffice
• Ensure the clickable area's purpose is clear from its immediate content
• Keep primary actions close to their related content

Required Accessibility Patterns

Keyboard Navigation and Interaction

• All interactive elements must support full keyboard navigation using standard keys:
• Tab, Shift+Tab, Enter, Escape, Arrow keys
• Do not remove focus styles. Prefer the native focus ring; if customizing, ensure the indicator remains clearly visible (including at 400% zoom) and has sufficient contrast.

WCAG 2.2 Additions to Keep in Scope (Layered + Often Manual)

In addition to WCAG 2.0/2.1 patterns, keep these WCAG 2.2 criteria in view:

• 2.4.11 Focus Not Obscured (Minimum) (AA) When an element receives keyboard focus, it must not be hidden by author-created content (e.g., sticky headers/footers, cookie banners, dialogs). If you implement sticky UI, ensure focused controls remain visible without requiring pointer input.

• 2.5.7 Dragging Movements (AA) If a feature uses drag-and-drop, provide a non-drag alternative (e.g., buttons to move items, keyboard-accessible reorder controls).

• 2.5.8 Target Size (Minimum) (AA) Minimum 24×24 CSS px for pointer targets (covered below). This often requires design/system consideration; treat failures as high-priority usability defects.

• 3.2.6 Consistent Help (A) If help mechanisms exist (support link, chat, help text), keep location/order consistent across pages.

• 3.3.7 Redundant Entry (A) Avoid requiring users to re-enter information previously provided in the same process (unless essential). Prefer auto-fill, prepopulation, or selectable options.

• 3.3.8 Accessible Authentication (Minimum) (AA) Authentication should not rely on cognitive function tests (e.g., remembering a password) without an accessible alternative (e.g., password managers supported, magic links, WebAuthn/passkeys, copy/paste allowed).

Note: Several of these are difficult to guarantee via static rules alone; they require targeted manual verification during testing/validation.

Touch Targets

All interactive elements should meet a minimum touch target size of 24×24 CSS px to align with WCAG 2.2 (SC 2.5.8 Target Size (Minimum), AA). Larger sizing (such as 44×44) is recommended for usability across Web, iOS, and Android.

Touch Target Requirements:

1. Minimum: 24×24 CSS px (WCAG 2.2 AA)
2. Preferred: 44×44 (common platform/usability guidance; WCAG AAA technique context)
3. Exception: When UI constraints make larger targets impossible, never go below 24×24

Text Resize:

All content must support up to 200% text resizing:

• Use relative units like em and rem.

Buttons:

Use native button elements instead of fake button elements:

• Use <button> instead of <div> or <span> for clickables.

Label in Name:

Ensure the visible text label is included in the accessible name to support screen readers and voice control per WCAG 2.1 Success Criterion 2.5.3.

• Use <label for="id">Visible Label</label> or ensure aria-label includes the same visible text. Avoid using placeholder-only text for labeling. Use aria-labelledby when combining multiple text elements as the label.

400% Zoom

Layouts must remain functional and readable at up to 400% zoom or scale:

• Support zoom with responsive grids and avoid horizontal scrolling.
• iOS/Android: Avoid fixed layouts that clip or overflow when scaling is increased.

Live Regions / Dynamic Updates

Auto-updating or dynamic content must be controllable and announced appropriately

• It may be up to the consumer of Arrow to manage dynamic updates
  • Web: Use ARIA live regions and visible controls (e.g., pause buttons).

Text Contrast

• Do not rely on color alone to convey meaning—include labels, icons, or visible states.
• Always show visible focus indicators on focusable elements. Use the default focus indicator.
• Text contrast must meet minimums:
  • 4.5:1 for normal text (defined as up to and including 18.5px regular or 14pt bold)
  • 3:1 for large text (≥18pt or ≥14pt bold)
  • 3:1 for non-text UI elements (e.g., icons, focus indicators, input borders, and buttons) against adjacent background

Focus indicator quality (recommended):

• Beyond “focus is visible”, ensure the focus indicator is easy to perceive (size + contrast). WCAG 2.2 adds stronger expectations via Focus Appearance (AAA). Even when only aiming for AA, treat weak focus styling as a defect that impedes keyboard users.

Non-text Contrast:

Ensure non-text elements have sufficient color contrast.

• Non-text elements that are not decorative should meet a contrast ration minimum of 3:1

Text Alternatives

• Non-text elements (e.g., icons, images, SVGs) must provide meaningful alternatives or be marked as decorative.
  • Before implementing any image-related accessibility:
    • Always explicitly ask whether an image is decorative or informative
    • Never assume an image needs alt text - this decision must come from the development team
    • Document the reasoning for treating an image as decorative or informative
  • Web: Use alt, aria-label, or aria-labelledby, or mark as decorative.
    • Informative image:
      • Use alt for <img> e.g. <img alt="some description">
    • Use aria-label or aria-labelledby for non-image elements (e.g., SVGs, icons)
    • Decorative image:
      • Use empty/null alt value for <img> e.g. <img alt="">
      • Use aria-hidden="true" for non-image elements (e.g., SVGs, icons) that are purely decorative

Important Note on Content Decisions

The decision about whether an image is decorative or informative must be made by the development team. Copilot should not make assumptions about:

• Image purpose (decorative vs informative)
• Alt text content
• The need for additional ARIA labels on semantic elements

When encountering images or interactive elements, Copilot should:

1. Maintain existing alt text if present
2. Keep empty alt attributes if already specified
3. Ask for clarification if the accessibility purpose is unclear
4. Suggest proper syntax once the purpose is determined by the developer

Headings

All platforms should use headings for large text that breaks up chunks of content.

• Use semantic HTML heading tags (<h1>–<h6>) in a logical, nested order. Do not skip levels (e.g., <h1> to <h4>). Never use <div> or <span> as visual-only headers. Avoid empty or generic headings.

Forms - Labels

All form fields should have labels in the code. - Use semantic HTML elements before applying ARIA roles. - All form fields must have programmatic labels: - Use <label for=""> or aria-labelledby - Placeholders must not be used as the only label

Forms - Errors & Helper Text

All form inputs must programmatically associate labels and helper text:

• Use aria-describedby or visually-associated text.

Error validation:

Errors need to be programmatically associated with each form field. Avoid automatically announcing errors as live regions.

• Use aria-describedby to link error messages to the form fields. Place the error text near the input and avoid using aria-live unless the error is critical and not tied to specific fields.

Error Announcement Priority:

1. Field-specific errors: Use aria-describedby to associate with inputs
2. Form-level errors: Use live regions only for critical, global error messages
3. Never use live regions for individual field validation

List Structure

This section describes how important list structure can be for users with disabilities

• Use native <ul> <ol> lists over <div>.

Reduced Motion:

Platforms should respect reduced motion settings to accommodate users with motion sensitivity.

• Use the prefers-reduced-motion media query to limit or disable animations, e.g., @media (prefers-reduced-motion: reduce) { animation: none; }.

Windows High Contrast Mode:

Using system colors ensures compatibility with Windows High Contrast Mode (Forced Colors) for better accessibility. This is really only needed for important things like component state or important component visual boundaries.

• Use system color keywords (e.g., ButtonText, Highlight, CanvasText) in CSS and detect forced colors with @media (forced-colors: active) {}.

Cards

For card components that do not have multiple CTAs in them or that have large touch targets, instead of wrapping the entire card, consider nesting a link inside a heading if the card has one. Create a large click area using pseudo selectors from that link inside the heading.

Good example

<div class="card">
    <h2><a href="#">Some cool heading</a></h2>
    <!-- rest of card contents -->
</div>

Copilot Response Requirements

Copilot-generated content must include:

1. Valid, accessible code using Arrow Design System components.
2. Inline comments explaining:
   • The purpose of accessibility features
   • Any trade-offs or browser quirks addressed
3. A plain-language summary of accessibility rationale.
4. A checklist that confirms rule conformance, for traceability
5. Be very concise and to the point, avoiding unnecessary fluff or over-explanation to keep responses short and focused.

Accessibility Verification:

• Keyboard-accessible interaction
• Visible focus indicators retained
• Valid labeling (aria-labelledby / label)
• Contrast ratios ≥ 4.5:1
• Proper ARIA use