Perceivable principals include:
- Visually impaired users must be able to receive information via sound or touch
- Hearing impaired users must be able to receive information via sight
- Low vision users must be able to receive information with alternative formatting or zoomed to larger sizes
- Color deficient users must be able to receive information without the use of color
Guideline 1.1
Text Alternatives: Provide text alternatives for any non-text content.
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Guideline Number |
Level |
Recommendations |
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1.1.1 Provide Text Alternatives for Any Non-text Content
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A |
All images, form image buttons, and image map hot spots have appropriate, equivalent alternative text. Images that do not convey content, are decorative, or contain content that is already conveyed in text are given null alt text (alt="") or implemented as CSS backgrounds. All linked images have descriptive alternative text. Equivalent alternatives to complex images are provided in context or on a separate (linked and/or referenced via longdesc) page. Form buttons have a descriptive value. Form inputs have associated text labels. Embedded multimedia is identified via accessible text. Frames are appropriately titled. |
Guideline 1.2
Time-based Media: Provide alternatives for time-based media
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Guideline Number |
Level |
Recommendations |
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1.2.1 Prerecorded Audio-only and Video-only
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A |
A descriptive text transcript (including all relevant visual and auditory clues and indicators) is provided for non-live, web-based audio (audio podcasts, MP3 files, etc.). A text or audio description is provided for non-live, web-based video-only (e.g., video that has no audio track). |
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A |
Synchronized captions are provided for non-live, web-based video (YouTube videos, etc.) |
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A |
A descriptive text transcript OR audio description audio track is provided for non-live, web-based video |
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AA |
Synchronized captions are provided for all live multimedia that contains audio (audio-only broadcasts, webcasts, video conferences, Flash animations, etc.) |
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AA |
Audio descriptions are provided for all video content NOTE: Only required if the video conveys content visually that is not available in the default audio track. |
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AAA |
A sign language video is provided for all media content that contains audio. |
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AAA |
When an audio description track cannot be added to video due to audio timing (e.g., no pauses in the audio), an alternative version of the video with pauses that allow audio descriptions is provided. |
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AAA |
A descriptive text transcript is provided for all pre-recorded media that has a video track. |
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AAA |
A descriptive text transcript (e.g., the script of the live audio) is provided for all live content that has audio. |
Guideline 1.3
Adaptable: Create content that can be presented in different ways (for example simpler layout) without losing information or structure
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Guideline Number |
Level |
Recommendations |
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|
A |
Semantic markup is used to designate headings (<h1>), lists (<ul>, <ol>, and <dl>), emphasized or special text (<strong>, <code>, <abbr>, <blockquote>, for example), etc. Semantic markup is used appropriately. Tables are used for tabular data. Where necessary, data cells are associated with their headers. Data table captions and summaries are used where appropriate. Text labels are associated with form input elements. Related form elements are grouped with field-set/legend. |
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A |
The reading and navigation order (determined by code order) is logical and intuitive. |
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A |
Instructions do not rely upon shape, size, or visual location (e.g., "Click the square icon to continue" or "Instructions are in the right-hand column"). Instructions do not rely upon sound (e.g., "A beeping sound indicates you may continue."). |
Guideline 1.4
Distinguishable: Make it easier for users to see and hear content including separating foreground from background
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Guideline Number |
Level |
Recommendations |
|
A |
Color is not used as the sole method of conveying content or distinguishing visual elements. Color alone is not used to distinguish links from surrounding text unless the luminance contrast between the link and the surrounding text is at least 3:1 and an additional differentiation (e.g., it becomes underlined) is provided when the link is hovered over or receives focus. |
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A |
A mechanism is provided to stop, pause, mute, or adjust volume for audio that automatically plays on a page for more than 3 seconds. |
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AA |
Text and images of text have a contrast ratio of at least 4.5:1. Large text (over 18 point or 14 point bold) has a contrast ratio of at least 3:1 |
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AA |
The page is readable and functional when the text size is doubled |
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AA |
If the same visual presentation can be made using text alone, an image is not used to present that text. |
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AAA |
Text and images of text have a contrast ratio of at least 7:1. Large text (over 18 point or 14 point bold) has a contrast ratio of at least 4.5:1 |
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AAA |
Audio of speech has no or very low background noise so the speech is easily distinguished. |
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AAA |
Blocks of text over one sentence in length: Are no more than 80 characters wide. Are NOT fully justified (aligned to both the left and the right margins). Have adequate line spacing (at least 1/2 the height of the text) and paragraph spacing (1.5 times line spacing). Have a specified foreground and background color. These can be applied to specific elements or to the page as a whole using CSS (and thus inherited by all other elements). Do NOT require horizontal scrolling when the text size is doubled. |
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AAA |
Text is used within an image only for decoration (image does not convey content) OR when the information cannot be presented with text alone. |