Low vision

Level A, 9 rules

• 1.2.3 Audio Description or Media Alternative (Prerecorded)

  Blind and low-vision viewers hear the soundtrack and miss the on-screen text, the actions and the context a sighted viewer picks up without noticing. People with cognitive disabilities who find it hard to work out what is happening on screen benefit from hearing the same thing named aloud.

• 1.3.3 Sensory Characteristics

  Blind users have nothing to search for when a control is identified only by where it sits. Colorblind users cannot find "the green one". Screen magnifier users see a small slice of the layout at a time, so "top right" means the top right of what they can currently see rather than of the page.

• 1.4.1 Use of Color

  Colorblind users, roughly 8% of men and 0.5% of women, are the group this rule was written for, and most of them use no assistive technology at all. Low-vision users and older users hit the same wall whenever a difference is carried by hue. So does anyone on a monochrome or limited-color display, an e-ink reader, or a phone in harsh sunlight.

• 2.1.1 Keyboard

  This affects blind users driving a screen reader from the keyboard, speech-input users whose software sends keystrokes on their behalf, people using sip-and-puff systems, on-screen keyboards, scanning software or an alternate keyboard, people with tremors or limited hand dexterity, and low-vision users who find tracking a pointer harder than pressing a key.

• 2.2.2 Pause, Stop, Hide

  This affects people with ADHD and other cognitive disabilities, people with vestibular disorders who get dizzy or nauseous from on-screen motion, screen-magnifier users trying to track a target that keeps moving, screen-reader users whose linear read is interrupted by content changing underneath them, and anyone who reads stationary text slowly.

• 2.4.1 Bypass Blocks

  This affects keyboard and switch users, who would otherwise press Tab dozens of times on every page, screen-reader users jumping by landmark or heading, screen-magnifier users hunting for where the main content starts, and people for whom repeated keystrokes are physically painful.

• 2.4.3 Focus Order

  This affects keyboard and screen-reader users moving through the page in sequence, magnification users at high zoom who can read a field in the wrong context entirely, and people with reading or cognitive disabilities who lose their place when focus lands somewhere unexpected.

• 3.2.2 On Input

  Screen reader users learn about a context change only once it has happened, because nothing warned them. People with low vision may not see a new window appear at all. People with reading or intellectual disabilities, and anyone who finds visual cues hard to read, need the change said in words rather than shown. Users with cognitive disabilities lose their thread when the page acts without being asked.

• 3.3.2 Labels or Instructions

  Users with cognitive disabilities lose the instruction the instant its placeholder disappears, and they are the people least able to rebuild it from memory. Screen reader users meet a field that was never labeled at all. People with low vision struggle with placeholder text in particular, since browsers usually render it at a contrast that would fail the contrast rule if it were ordinary text. And everybody guesses at date formats nobody stated.

Level AA, 14 rules

• 1.2.5 Audio Description (Prerecorded)

  Blind and low-vision viewers depend on the soundtrack to carry everything the video communicates, because nothing on screen reaches them any other way. Viewers with cognitive disabilities who find it hard to interpret what is happening on screen get the same benefit from hearing it named.

• 1.3.4 Orientation

  Users with motor disabilities whose device is mounted in a fixed position, on a wheelchair arm or a bed frame, cannot rotate it at all. Anyone using a stand or a dock that holds one orientation is in the same position. Low-vision users who read in landscape to fit more words on a line lose that option too.

• 1.4.3 Contrast (Minimum)

  Low-vision users depend on sufficient contrast most directly. Older users lose contrast sensitivity gradually, and that loss is the thing the 4.5:1 figure was calculated from. Colorblind users are affected too, though not through hue, since the formula deliberately ignores hue. And everyone reading a phone in daylight is running the same test your auditor is.

• 1.4.4 Resize Text

  Low-vision users who browse at 200% or higher every single day meet the failure before anyone else does. Older users run into it gradually as close focus goes. Anyone on a high-density screen with scaled text, and anyone pinch-zooming a phone, hits the same wall when a page blocks the zoom.

• 1.4.5 Images of Text

  Low-vision users who zoom in or apply a custom stylesheet lose the words first. Dyslexic readers who swap in a different font lose them too. People with visual tracking difficulties who change line spacing and alignment cannot change either one inside an image. Users of browser translation tools get a page in their language with a picture still in yours.

• 1.4.10 Reflow

  Low-vision users browsing at high magnification meet this every day, and 400% zoom is an ordinary setting rather than an extreme one. Small-screen users get the same layout for a different reason. Anyone with a browser window docked to half a display is closer to the test viewport than they think, since 960 pixels at 300% zoom is already 320.

• 1.4.11 Non-text Contrast

  Low-vision users lose pale form fields altogether, and a field they cannot find is a form they cannot fill. Older users hit the same edge, since contrast sensitivity falls with age. Keyboard users need to see where focus has landed, which is the same measurement applied to a different thing. Anyone on a dim or reflective screen runs your whole interface at lower effective contrast than you designed it for.

• 1.4.12 Text Spacing

  Low-vision readers who need bigger gaps between lines, words and letters to read at all. Dyslexic readers who widen spacing to read faster. Anyone using a reading-aid extension, a bookmarklet or a custom stylesheet, which is how these changes usually get made, because no mainstream browser offers all four settings for an ordinary page.

• 1.4.13 Content on Hover or Focus

  Screen magnifier users need to pan across the screen to read revealed content, and panning means moving the pointer. Users with tremor or low pointer accuracy trigger content they did not mean to and need a way to clear it. People who run a large mouse cursor find it covering the very thing that just appeared. Users with cognitive disabilities need the reading time a timer takes away.

• 2.4.5 Multiple Ways

  This affects people with cognitive disabilities who find deep hierarchies hard to hold in mind, screen-reader users for whom search beats a menu tree, magnification users reading a large navigation bar a slice at a time, and people who would rather move through a site in sequence, page after page.

• 2.4.11 Focus Not Obscured (Minimum)

  This affects sighted keyboard users who lose track of focus behind a sticky bar, low-vision users who orient with a pointer and see less of the page at a time under magnification, and people with attention limitations, short-term memory limitations or executive processing difficulties, who lose their place entirely when focus goes out of sight.

• 3.2.3 Consistent Navigation

  Screen reader users move through a page in sequence, so a link that has moved is a link they now have to hunt for. People with low vision using magnification see a small window of the screen at a time and rely on the layout holding still. Users with cognitive and intellectual disabilities depend on the routine staying put. And sighted users with no disability at all navigate by spatial memory too, which is why this one turns up in usability testing as well as in audits.

• 3.3.3 Error Suggestion

  People with cognitive and learning disabilities are hit hardest, because knowing something is wrong is not the same as knowing what to do. Blind and low-vision users need the fix described rather than shown, since the field will not look wrong to them. People with motor impairments pay for every extra attempt in effort. Everybody else is stuck in the same loop with less at stake.

• 4.1.3 Status Messages

  Screen reader users add something to the cart, apply a filter, or submit a form, and hear nothing back, so they have no way to know whether anything happened. Blind and low-vision users of assistive technology are the audience the criterion names. There is a second benefit further out. Software that can identify a status message can also hold it back, delay it, or push it forward for a user who wants that. None of it is possible until the message is marked.

Level AAA, 12 rules

No law names AAA as a blanket duty, but these are where the remaining barriers for people who can see the screen but not easily usually sit.

• 1.2.7 Extended Audio Description (Prerecorded)

  Blind viewers and people with low vision who cannot see the screen feel this first, and W3C names a third group beside them. People with cognitive disabilities who find it hard to work out what is happening visually.

• 1.4.6 Contrast (Enhanced)

  People with low vision and people with reduced contrast sensitivity gain most, and older readers are the group W3C names when it explains where the numbers came from.

• 1.4.8 Visual Presentation

  People with dyslexia, low vision and other reading difficulties benefit most, and W3C attributes the justification problem specifically to certain cognitive disabilities.

• 1.4.9 Images of Text (No Exception)

  People with low vision, people with visual tracking difficulties, and people with cognitive disabilities that affect reading are the three groups W3C names.

• 2.2.3 No Timing

  W3C names blind readers first, then people with low vision, then people with cognitive limitations and people with motor impairments, and adds deaf readers for whom written text is a second language.

• 2.2.4 Interruptions

  People with attention differences feel this most, along with screen reader users and people with low vision whose reading gets cut across by an update they never asked for.

• 2.4.12 Focus Not Obscured (Enhanced)

  Sighted keyboard users are the main group, and that includes people using speech input, sip-and-puff switches, on-screen keyboards and scanning software. People with low vision using magnification, and people with attention or short-term memory limitations, are the other two W3C names.

• 2.5.5 Target Size (Enhanced)

  People with tremor or reduced dexterity, people with large fingers or tapping with a knuckle, anybody using a phone one-handed, and anybody tapping on a moving bus. W3C names low vision too, since a bigger target is easier to see as well as to hit.

• 3.1.3 Unusual Words

  People with cognitive and learning disabilities who find words hard to decode or to understand. W3C names a third group that surprises people, readers using a screen magnifier, who lose the surrounding context that would otherwise settle the meaning.

• 3.1.4 Abbreviations

  People who find words hard to decode, people with limited memory, people who struggle to use context, and readers using a screen magnifier, who lose the surrounding text that would otherwise explain the term.

• 3.1.6 Pronunciation

  Blind readers, readers with low vision, and readers with reading disabilities are the three groups W3C names, along with anybody whose technology reads the words out loud.

• 3.2.5 Change on Request

  Screen reader users, people with low vision, people with motor impairments and people with cognitive limitations are the four groups W3C names.

Other groups

• Blind and screen reader users40 rules
• Deaf and hard of hearing9 rules
• Motor and keyboard-only33 rules
• Voice control13 rules
• Cognitive and learning50 rules
• Seizures and vestibular disorders4 rules