WCAG 2.1
WCAG 2.1 success criteria, explained without jargon
WCAG 2.1 has 78 success criteria organised under four principles: Perceivable, Operable, Understandable, Robust. Each one is a single rule. Getting them right does not require reading the W3C spec end to end — it requires knowing which ones break most often on real sites. Start with the criteria below; they cover the failures we see in the majority of audits.
Perceivable
1.1.1 Non-text Content
Level AAll non-text content (images, icons, controls) must have a text alternative that serves the equivalent purpose.
1.3.1 Info and Relationships
Level AThe visual structure of a page (headings, lists, tables, form labels) must also be available programmatically — assistive tech relies on the markup, not the styling.
1.4.3 Contrast (Minimum)
Level AABody text must have a contrast ratio of at least 4.5:1 against its background. Large text (18pt+, or 14pt bold) needs at least 3:1.
1.4.11 Non-text Contrast
Level AAUI components (form borders, focus indicators, icons that convey meaning) must have at least a 3:1 contrast ratio against adjacent colors.
1.2.2 Captions (Prerecorded)
Level ACaptions must be provided for all prerecorded audio in synchronized media.
1.4.4 Resize Text
Level AAText must be resizable to 200% without loss of content or functionality.
1.4.10 Reflow
Level AAContent must reflow to a 320 CSS pixel width (the equivalent of 400% zoom on a 1280px viewport) without requiring horizontal scrolling for the primary reading direction.
1.3.5 Identify Input Purpose
Level AAInputs collecting common personal information must have a programmatic purpose set, typically via the autocomplete attribute.
1.4.13 Content on Hover or Focus
Level AATooltip and hover content must be dismissible (Esc), hoverable (mouse can move into it), and persistent (stays until dismissed).
1.2.1 Audio-only and Video-only (Prerecorded)
Level AFor prerecorded audio-only content, provide a transcript. For prerecorded video-only content, provide either a transcript or an audio description.
1.2.3 Audio Description or Media Alternative (Prerecorded)
Level APrerecorded synchronised media must have either an audio description or a full media alternative.
1.2.4 Captions (Live)
Level AALive audio in synchronised media must have captions.
1.3.2 Meaningful Sequence
Level AWhen the sequence in which content is presented affects its meaning, a correct reading sequence must be programmatically determinable.
1.3.3 Sensory Characteristics
Level AInstructions must not rely solely on sensory characteristics like shape, color, size, position, or sound.
1.4.1 Use of Color
Level AColor must not be the only visual means of conveying information, indicating an action, or distinguishing a visual element.
1.4.2 Audio Control
Level AIf audio plays automatically for more than 3 seconds, a way to pause, stop, or control its volume independently of system volume must be provided.
1.4.5 Images of Text
Level AAIf the technologies used can achieve the visual presentation, text must not be replaced by an image of text.
1.4.12 Text Spacing
Level AAWhen users override line height to 1.5×, paragraph spacing to 2×, letter spacing to 0.12×, and word spacing to 0.16×, no content or functionality must be lost.
Operable
2.1.1 Keyboard
Level AEvery interactive function on the page must be operable using only the keyboard.
2.1.2 No Keyboard Trap
Level AKeyboard focus must never get trapped — users must always be able to navigate away using standard keys.
2.4.3 Focus Order
Level AComponents must receive focus in an order that preserves meaning and operability — usually matching the visual reading order.
2.4.4 Link Purpose (In Context)
Level AThe purpose of every link must be clear from its link text, or from its text combined with the surrounding context.
2.4.6 Headings and Labels
Level AAHeadings and labels must describe the topic or purpose of the content they introduce.
2.4.7 Focus Visible
Level AAAny keyboard-operable interface must have a visible indicator showing which element has focus.
2.2.2 Pause, Stop, Hide
Level AAny auto-starting moving, blinking, or scrolling content lasting longer than 5 seconds must be pausable, stoppable, or hideable.
2.4.1 Bypass Blocks
Level AA mechanism is available to bypass blocks of content that are repeated on multiple pages.
2.5.3 Label in Name
Level AFor UI components with labels that include text, the accessible name must contain the visible label text.
2.1.4 Character Key Shortcuts
Level ASingle-character keyboard shortcuts must be turn-offable, remappable, or only active when the relevant control has focus.
2.2.1 Timing Adjustable
Level AFor each time limit set by the content, the user must be able to turn it off, adjust it, or extend it.
2.3.1 Three Flashes or Below Threshold
Level AContent must not flash more than three times in any one-second period, or the flash must stay below the general flash and red flash thresholds.
2.4.2 Page Titled
Level AWeb pages must have titles that describe topic or purpose.
2.5.2 Pointer Cancellation
Level AFor functionality operated using a single pointer, completion of the action must occur on the up-event, not the down-event.
2.5.4 Motion Actuation
Level AFunctionality operated by device motion (shake, tilt) must also be operable by conventional UI controls and motion actuation must be disableable.
Understandable
3.1.1 Language of Page
Level AThe default human language of the page must be programmatically set via the lang attribute on <html>.
3.3.1 Error Identification
Level AWhen an input error is detected, the field in error and the description of the error must be conveyed in text.
3.3.2 Labels or Instructions
Level ALabels or instructions must be provided when content requires user input.
3.2.1 On Focus
Level AWhen any component receives focus, it must not initiate a change of context.
3.2.2 On Input
Level AChanging the setting of any component must not automatically cause a change of context unless the user has been warned.
Robust
Looking for a starting point? If you only have time for ten criteria, fix 1.1.1, 1.3.1, 1.4.3, 2.1.1, 2.4.3, 2.4.4, 2.4.7, 3.3.2, 4.1.2, and 4.1.3. Those ten are responsible for the bulk of issues automated scanners flag and the bulk of complaints regulators receive.
Want deeper context on how the four principles fit together? The complete WCAG 2.1 guide covers POUR, conformance levels, legal requirements, and testing tools.
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