WCAG 2.1 Reference
Web Content Accessibility Guidelines — the international web accessibility standard. Requirements increase from A → AA → AAA.
4 Principles (POUR)
Information and UI components must be presentable to users in ways they can perceive.
UI components and navigation must be operable.
Information and the operation of the user interface must be understandable.
Content must be robust enough to be reliably interpreted by a wide variety of user agents, including assistive technologies.
Conformance levels
The minimum level. Failing to meet these criteria means some users cannot access content at all.
| Criterion | Title | Requirement |
|---|---|---|
| 1.1.1 | Non-text Content | Provide alt text for all non-text content (images, icons). |
| 1.3.1 | Info and Relationships | Use HTML structure (headings, lists, tables) to convey visual structure in code. |
| 2.1.1 | Keyboard | All functionality must be accessible using only a keyboard. |
| 2.4.2 | Page Titled | Each page must have a unique title that describes its topic. |
| 3.1.1 | Language of Page | Specify the document language using the html[lang] attribute. |
| 4.1.1 | Parsing | No HTML markup errors (duplicate IDs, unclosed tags, etc.). |
| 4.1.2 | Name, Role, Value | Expose role, aria-label, aria-expanded, and other states for UI components. |
The de-facto standard. Most laws and corporate policies require AA conformance. This project targets AA.
| Criterion | Title | Requirement |
|---|---|---|
| 1.4.3 | Contrast (Minimum) | Normal text 4.5:1, large text 3:1 minimum contrast ratio. |
| 1.4.4 | Resize Text | Content and functionality must be maintained when zoomed to 200%. |
| 1.4.11 | Non-text Contrast | UI components (icons, focus rings, form borders) must meet 3:1 contrast. |
| 1.4.12 | Text Spacing | No loss of content when line height, letter spacing, word spacing, or paragraph spacing is changed. |
| 1.4.13 | Content on Hover or Focus | Content that appears on hover or focus (like tooltips) must be dismissible and persistent. |
| 2.4.6 | Headings and Labels | Headings and labels must describe topic or purpose. |
| 2.4.7 | Focus Visible | A visible focus indicator must be shown when navigating by keyboard. |
| 3.2.3 | Consistent Navigation | Repeated navigation must appear in the same order across pages. |
| 3.3.1 | Error Identification | When an error occurs, describe which item is wrong and why, in text. |
| 3.3.2 | Labels or Instructions | Provide labels or instructions for user input. |
The highest level. Difficult to apply to all content universally — applied selectively in specific contexts.
| Criterion | Title | Requirement |
|---|---|---|
| 1.4.6 | Contrast (Enhanced) | Normal text 7:1, large text 4.5:1 minimum contrast ratio. |
| 2.1.3 | Keyboard (No Exception) | All functionality usable by keyboard, including path-dependent interactions. |
| 2.2.3 | No Timing | No time limits on any functionality, unless the timing is essential. |
| 2.4.9 | Link Purpose (Link Only) | Avoid ambiguous link text like "Read more" — link purpose must be clear from the link alone. |
| 3.1.3 | Unusual Words | Provide definitions for jargon, idioms, and specialized terminology. |
| 3.3.6 | Error Prevention (All) | All input forms must provide review, confirmation, or reversal of submissions. |
Full specification: W3C WCAG 2.1