Table 5 Web Content Accessibility Guidelines (WCAG) principles, guidelines, and examples of success criteria and their levels (Note: this is not an exhaustive list)

1. Perceivable information and user interface

1.1 Text alternatives for non-text content

1.1.1 Non-text content: All non-text content that is presented to the user has a text alternative that serves the equivalent purpose except for a short list of exceptions with individual success criteria (e.g., If non-text content is a control or accepts user input, then it has a name that describes its purpose.)

(Level A)

1.2 Captions and other alternatives for multimedia

1.2.2 Captions (prerecorded): Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such. (Level A)

1.2.5 Audio description (prerecorded): Audio description is provided for all prerecorded video content in synchronized media. (Level AA)

1.2.6 Sign language (prerecorded): Sign language interpretation is provided for all prerecorded audio content in synchronized media. (Level AAA)

1.3 Adaptable: content can be presented in different ways without losing information or structure

1.3.1 Info and relationships: Information, structure, and relationships conveyed through presentation can be programmatically determined or are available as text (Level A)

1.3.2 Meaningful sequence: When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined. (Level A)

1.3.3 Sensory characteristics: Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, size, visual location, orientation, or sound. (Level A)

1.4 Distinguishable: content is easier to see and hear

1.4.1 Use of color: Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. (Level A)

1.4.3 Contrast (minimum): The visual presentation of text and images of text has a contrast of at least 4.5:1, except for large-scale text, incidental text (e.g., pure decoration), and logotypes. (Level AA)

1.4.4 Resize text: Except for captions and images of text, text can be resized without assistive technology up to 200% without loss of content or functionality. (Level AA)

1.4.9 Images of text (no exception): Images of text are only used for pure decoration or where a particular presentation of text is essential to the information being conveyed. (Level AAA)

2. Operable user interface and navigation

2.1 Keyboard accessible: Functionality is available from a keyboard

2.1.1 Keyboard: All functionality of the content that is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user’s movement and not just the end points. (Level A)

2.1.2 No keyboard trap: If keyboard focus can be moved to a component of the page using a keyboard interface, then focus can be moved away from that component using only a keyboard interface, and, if it requires more than unmodified arrow or tab keys or other standard exit methods, the user is advised of the method for moving focus away. (Level A)

2.2 Enough time: Users have enough time to read and use the content

2.2.2 Pause, stop, hide: For moving, blinking, scrolling, or auto-updating information, all of the following are true: (1) starts automatically, (2) lasts more than 5 s, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it unless the movement, blinking, or scrolling is part of an activity where it is essential. (Level A)

2.2.5 Re-authenticating: When an authenticated session expires, the user can continue the activity without loss of data after re-authenticating.

(Level AAA)

2.3 Seizures: Content does not cause seizures

2.3.1 Three flashes or below threshold: Webpages do not contain anything that flashes more than three times in any 1-s period, or the flash is below the general flash and red flash thresholds. (Level A)

2.3.2 Three flashes: Webpages do not contain anything that flashes more than three times in any 1-s period. (Level AAA)

2.4 Navigable: Users can easily navigate, find content, and determine where they are on a webpage

2.4.1 Bypass blocks: A mechanism is available to bypass blocks of content that are repeated on multiple webpages. (Level A)

2.4.2 Page titled: Webpages have titles that describe topic or purpose. (Level A)

2.4.3 Focus order: If a webpage can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability. (Level A)

2.4.4 Link purpose (in context): The purpose of each link can be determined from the link text alone or from the link text together with its programmatically determined link context, except where the purpose of the link would be ambiguous to users in general. (Level A)

2.4.6 Headings and labels: Headings and labels describe topic or purpose. (Level AA)

3. Understandable information and user interface

3.1 Readable: Text is readable and understandable

3.1.1 Language of page: The default human language of each webpage can be programmatically determined. (Level A)

3.1.3 Unusual words: A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon. (Level AAA)

3.1.4 Abbreviations: A mechanism for identifying the expanded form of meaning of abbreviations is available. (Level AAA)

3.2 Predictable: Content appears and operates in predictable ways

3.2.1 On focus: When any component receives focus, it does not initiate a change of context.

(Level A)

3.2.2 On input: Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component. (Level A)

3.2.4 Consistent identification: Components that have the same functionality within a set of webpages are identified consistently. (Level AA)

3.3 Input assistance: Users are helped to avoid and correct mistakes

3.3.1 Error identification: If an input error is automatically detected, the item that is in error is identified and the error is described to the user in text. (Level A)

3.3.2 Labels or instructions: Labels or instructions are provided when content requires user input. (Level A)

3.3.3 Error suggestion: If an input error is automatically detected and suggestions for the correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content. (Level AA)

3.3.6 Error prevention (all): For webpages that require the user to submit information, at least of the following is true: (1) Reversible: Submissions are reversible. (2) Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them. (3) Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission. (Level AAA)

4. Robust content and reliable information

4.1 Compatible: Content is compatible with current and future user tools

4.1.1. Parsing: In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features. (Level A)

4.1.2 Name, role, value: For all user interface components, the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically set; and notification of changes to these items is available to user agents, including assistive technologies. (Level A)