WCAG 2.1 guidelines

The guidelines for making web content accessible to as wide an audience as possible.

Web Content Accessibility Guidelines (WCAG) 2.1

Web Content Accessibility Guidelines (WCAG) 2.1 contain a large number of recommendations to make web content more accessible. Following these guidelines will make content more accessible to people with disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive disabilities, motor disabilities, speech difficulties, light sensitivity, and combinations thereof. Following these guidelines also makes web content more usable for users in general.

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Principle 1. Perceivable

Information and user interface components must be presentable to users in ways they can perceive.

Guideline 1.1 Text alternatives

Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.

1.1.1 Non-text Content

Level A

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below.

Controls, Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to Success Criterion 4.1.2 for additional requirements for controls and content that accepts user input.)

Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2 for additional requirements for media.)

Test: If non-text content is a test or exercise that would be invalid if presented in text, then text alternatives at least provide descriptive identification of the non-text content.

Sensory: If non-text content is primarily intended to create a specific sensory experience, then text alternatives at least provide descriptive identification of the non-text content.

CAPTCHA: If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.

Decoration, Formatting, Invisible: If non-text content is pure decoration, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.

Understanding Non-text Content
How to Meet Non-text Content

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Guideline 1.2 Time-based media

Provide alternatives for time-based media.

1.2.1 Audio-only and video-only (Prerecorded)

Level A

For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labeled as such:

Understanding Audio-only and Video-only (Prerecorded)
How to Meet Audio-only and Video-only (Prerecorded)

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1.2.2 Captions (prerecorded)

Level A

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.

Understanding Captions (Prerecorded)
How to Meet Captions (Prerecorded)

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1.2.3 Audio Description or Media Alternative (Prerecorded)

Level A

An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such.

Understanding Audio Description or Media Alternative (Prerecorded)
How to Meet Audio Description or Media Alternative (Prerecorded)

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1.2.4 Captions (live)

Level AA

Captions are provided for all live audio content in synchronized media.

Understanding Captions (Live)
How to Meet Captions (Live)

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1.2.5 Audio Description (Prerecorded)

Level AA

Audio description is provided for all prerecorded video content in synchronized media.

Understanding Audio Description (Prerecorded)
How to Meet Audio Description (Prerecorded)

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1.2.6 Sign Language (Prerecorded)

Level AAA

Sign language interpretation is provided for all prerecorded audio content in synchronized media.

Understanding Sign Language (Prerecorded)
How to Meet Sign Language (Prerecorded)

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1.2.7 Extended Audio Description (Prerecorded)

Level AAA

Where pauses in foreground audio are insufficient to allow audio descriptions to convey the sense of the video, extended audio description is provided for all prerecorded video content in synchronized media.

Understanding Extended Audio Description (Prerecorded)
How to Meet Extended Audio Description (Prerecorded)

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1.2.8 Media Alternative (Prerecorded)

Level AAA

An alternative for time-based media is provided for all prerecorded synchronized media and for all prerecorded video-only media.

Understanding Media Alternative (Prerecorded)
How to Meet Media Alternative (Prerecorded)

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1.2.9 Audio-only (Live)

Level AAA

An alternative for time-based media that presents equivalent information for live audio-only content is provided.

Understanding Audio-only (Live)
How to Meet Audio-only (Live)

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Guideline 1.3 Adaptable

Create content that can be presented in different ways (for example simpler layout) without losing information or structure.

1.3.1 Info and Relationships

Level A

Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.

Understanding Info and Relationships
How to Meet Info and Relationships

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1.3.2 Meaningful Sequence

Level A

When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined.

Understanding Meaningful Sequence
How To Meet Meaningful Sequence 

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1.3.3 Sensory Characteristics

Level A

Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, color, size, visual location, orientation, or sound.

Understanding Sensory Characteristics
How to Meet Sensory Characteristics

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1.3.4 Orientation

Level AA

Content does not restrict its view and operation to a single display orientation, such as portrait or landscape, unless a specific display orientation is essential.

Understanding Orientation
How to Meet Orientation

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1.3.5 Identify Input Purpose

Level AA

The purpose of each input field collecting information about the user can be programmatically determined when:

Understanding Identify Input Purpose
How to Meet Identify Input Purpose

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1.3.6 Identify Purpose

Level AAA

In content implemented using markup languages, the purpose of user interface components, icons and regions can be programmaticaly determined.

Understanding Identify Purpose
How to Meet Identify Purpose

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Guideline 1.4 Distinguishable

Make it easier for users to see and hear content including separating foreground from background.

1.4.1 Use of Color

Level A

Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

Understanding Use of Color
How to Meet Use of Color

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1.4.2 Audio Control

Level A

If any audio on a Web page plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume independently from the overall system volume level.

Understanding Audio Control
How to Meet Audio Control

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1.4.3 Contrast (Minimum)

Level AA

The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following:

Understanding Contrast (Minimum)
How to Meet Contrast (Minimum)

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1.4.4 Resize Text

Level AA

Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality.

Understanding Resize Text
How to Meet Resize Text

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1.4.5 Images of Text

Level AA

If the technologies being used can achieve the visual presentation, text is used to convey information rather than images of text except for the following:

Understanding Images of Text
How to Meet Images of Text

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1.4.6 Contrast (Enhanced)

Level AAA

The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following:

Understanding Contrast (Enhanced)
How to Meet Contrast (Enhanced)

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1.4.7 Low or No Background Audio

Level AAA

For prerecorded audio-only content that (1) contains primarily speech in the foreground, (2) is not an audio CAPTCHA or audio logo, and (3) is not vocalization intended to be primarily musical expression such as singing or rapping, at least one of the following is true:

Understanding Low or No Backgrond Audio
How to Meet Low or No Background Audio

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1.4.8 Visual Presentation

Level AAA

For the visual presentation of blocks of text, a mechanism is available to achieve the following:

Understanding Visual Presentation
How to Meet Visual Presentation

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1.4.9 Images of Text (No Exception)

Level AAA

Images of text are only used for pure decoration or where a particular presentation of text is essential to the information being conveyed.

Understanding Images of Text (No Exceptions)
How to Meet Images of Text (No Exceptions)

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1.4.10 Reflow

Level AA

Content can be presented without loss of information or functionality, and without requiring scrolling in two dimensions for:

Except for parts of the content which require two-dimensional layout for usage or meaning.

Examples of content which requires two-dimensional layout are images required for understanding (such as maps and diagrams), video, games, presentations, data tables (not individual cells), and interfaces where it is necessary to keep toolbars in view while manipulating content. It is acceptable to provide two-dimensional scrolling for such parts of the content.

Understanding Reflow
How to Meet Reflow

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1.4.11 Non-text Contrast

Niveau AA

The visual presentation of the following have a contrast ratio of at least 3:1 against adjacent color(s):

User Interface Components: Visual information required to identify user interface components and states, except for inactive components or where the appearance of the component is determined by the user agent and not modified by the author;

Graphical Objects: Parts of graphics required to understand the content, except when a particular presentation of graphics is essential to the information being conveyed.

Understanding Non-text Contrast
How to Meet Non-text Contrast

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1.4.12 Text Spacing

Level AA

In content implemented using markup languages that support the following text style properties, no loss of content or functionality occurs by setting all of the following and by changing no other style property:

Exception: Human languages and scripts that do not make use of one or more of these text style properties in written text can conform using only the properties that exist for that combination of language and script.

Understanding Text Spacing
How to Meet Text Spacing

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1.4.13 Content on Hover or Focus

Level AA

Where receiving and then removing pointer hover or keyboard focus triggers additional content to become visible and then hidden, the following are true:

Exception: The visual presentation of the additional content is controlled by the user agent and is not modified by the author.

Understanding Content on Hover or Focus
How to Meet Content on Hover or Focus

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Principle 2. Operable

User interface components and navigation must be operable.

Guideline 2.1 Keyboard Accessible

Make all functionality available from a keyboard.

2.1.1 Keyboard

Level A

All functionality of the content 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 endpoints.

Understanding Keyboard
How to Meet Keyboard

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2.1.2 No Keyboard Trap

Level A

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.

Understanding No Keyboard Trap
How to Meet No Keyboard Trap

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2.1.3 Keyboard (No Exception)

Level AAA

All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes.

Understanding Keyboard (No Exception)
How to Meet Keyboard (No Exception)

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2.1.4 Character Key Shortcuts

Level A

If a keyboard shortcut is implemented in content using only letter (including upper- and lower-case letters), punctuation, number, or symbol characters, then at least one of the following is true:

Understanding Character Key Shortcuts
How to Meet Character Key Shortcuts

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Guideline 2.2 Enough Time

Provide users enough time to read and use content.

2.2.1 Timing Adjustable

Level A

For each time limit that is set by the content, at least one of the following is true:

Understanding Timing Adjustable
How to Meet Timing Adjustable

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2.2.2 Pause, Stop, Hide

Level A

For moving, blinking, scrolling, or auto-updating information, all of the following are true:

Understanding Pause, Stop, Hide 
How to Meet Pause, Stop, Hide

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2.2.3 No Timing

Level AAA

Timing is not an essential part of the event or activity presented by the content, except for non-interactive synchronized media and real-time events.

Understanding No Timing
How to Meet No Timing

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2.2.4 Interruptions

Level AAA

Interruptions can be postponed or suppressed by the user, except interruptions involving an emergency.

Understanding Interruptions
How to Meet Interruptions

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2.2.5 Re-authenticating

Level AAA

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

Understanding Re-authentication
How to Meet Re-authentication

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2.2.6 Timeouts

Level AAA

Users are warned of the duration of any user inactivity that could cause data loss, unless the data is preserved for more than 20 hours when the user does not take any actions.

Understanding Time-outs
How to Meet Time-outs

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Guideline 2.3 Seizures and Physical Reactions

Do not design content in a way that is known to cause seizures or physical reactions.

2.3.1 Three Flashes or Below Threshold

Level A

Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds.

Understanding Three Flashes or Below Thershold
How to Meet Three Flashes or Below Thershold

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2.3.2 Three Flashes

Level AAA

Web pages do not contain anything that flashes more than three times in any one second period.

Understanding Three Flashes
How to Meet Three Flashes

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2.3.3 Animation from Interactions

Level AAA

Motion animation triggered by interaction can be disabled, unless the animation is essential to the functionality or the information being conveyed.

Understanding Animation from Interactions
How to Meet Animation from Interactions

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Guideline 2.4 Navigable

Provide ways to help users navigate, find content, and determine where they are.

2.4.1 Bypass Blocks

Level A

A mechanism is available to bypass blocks of content that are repeated on multiple Web pages.

Understanding Bypass Blocks
How to Meet Bypass Blocks

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2.4.2 Page Titled

Level A

Web pages have titles that describe topic or purpose.

Understanding Page Titled
How to Meet Page Titled

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2.4.3 Focus Order

Level A

If a Web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability..

Understanding Focus Order
How to Meet Focus Order

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2.4.4 Link Purpose (In Context)

Level A

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.

Understanding Link Purpose (In Context)
How to Meet Link Purpose (in Context)

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2.4.5 Multiple Ways

Level AA

More than one way is available to locate a Web page within a set of Web pages except where the Web Page is the result of, or a step in, a process.

Understanding Multiple Ways
How to Meet Multiple Ways

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2.4.6 Headings and Labels

Level AA

Headings and labels describe topic or purpose.

Understanding Headings and Labels
How to Meet Headings and Labels

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2.4.7 Focus Visible

Level AA

Any keyboard operable user interface has a mode of operation where the keyboard focus indicator is visible.

Understanding Focus Visible
How to Meet Focus Visible

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2.4.8 Location

Level AAA

Information about the user’s location within a set of Web pages is available.

Understanding Location
How to Meet Location

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2.4.9  Link Purpose (Link Only)

Level AAA

A mechanism is available to allow the purpose of each link to be identified from link text alone, except where the purpose of the link would be ambiguous to users in general.

Understanding Link Purpose (Link Only)
How to Meet Link Purpose (Link Only)

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2.4.10 Section Headings

Level AAA

Section headings are used to organize the content.

Understanding Section Headings
How to Meet Section Headings

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2.5 Input Modalities

Make it easier for users to operate functionality through various inputs beyond keyboard.

2.5.1 Pointer Gestures

Level A

All functionality that uses multipoint or path-based gestures for operation can be operated with a single pointer without a path-based gesture, unless a multipoint or path-based gesture is essential.

Understanding Pointer Gestures
How to Meet Pointer Gestures

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2.5.2 Pointer Cancellation

Level A

For functionality that can be operated using a single pointer, at least one of the following is true:

Understanding Pointer Cancellation
How to Meet Pointer Cancellation

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2.5.3 Label in name

Level A

For user interface components with labels that include text or images of text, the name contains the text that is presented visually.

Understanding Label in name
How to Meet Label in name

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2.5.4 Motion Actuation

Level A

Functionality that can be operated by device motion or user motion can also be operated by user interface components and responding to the motion can be disabled to prevent accidental actuation, except when:

Understanding Motion Actuation
How to Meet Motion Actuation

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2.5.5 Target Size

Level AAA

The size of the target for pointer inputs is at least 44 by 44 CSS pixels except when:

Understanding Target Size
How to Meet Target Size

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2.5.6 Concurrent Input Mechanisms

Level AAA

Web content does not restrict use of input modalities available on a platform except where the restriction is essential, required to ensure the security of the content, or required to respect user settings.

Understanding Current Input Mechanisms
How to Meet Current Input Mechanisms

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Principle 3. Understandable

Information and the operation of the user interface must be understandable.

Guideline 3.1 Readable

Make text content readable and understandable.

3.1.1 Language of Page

Level A

The default human language of each Web page can be programmatically determined.

Understanding Language of Page
How to Meet Language of Page

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3.1.2 Language of Parts

Level AA

The human language of each passage or phrase in the content can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text.

Understanding Language of Parts
How to Meet Language of Parts

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3.1.3  Unusual Words

Level AAA

A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon.

Understanding Unusual Words
How to Meet Unusual Words

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3.1.4 Abbreviations

Level AAA

A mechanism for identifying the expanded form or meaning of abbreviations is available.

Understanding Abbreviations
How to Meet Abbreviations

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3.1.5 Reading Level

Level AAA

When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplementary content, or a version that does not require reading ability more advanced than the lower secondary education level, is available.

Understanding Reading Level
Hoe to Meet Reading Level

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3.1.6 Pronunciation

Level AAA

A mechanism is available for identifying specific pronunciation of words where meaning of the words, in context, is ambiguous without knowing the pronunciation.

Understanding Pronunciation
How to Meet Pronunciation

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Guideline 3.2 Predictable

Make web pages appear and operate in predictable ways.

3.2.1 On Focus

Level A

When any user interface component receives focus, it does not initiate a change of context.

Understanding on Focus
How to Meet On Focus

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3.2.2 On Input

Level A

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.

Understanding On Input
How to Meet On Input

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3.2.3 Consistent Navigation

Level AA

Navigational mechanisms that are repeated on multiple Web pages within a set of Web pages occur in the same relative order each time they are repeated, unless a change is initiated by the user.

Understanding Consistent Navigation
How to Meet Consistent Navigation

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3.2.4 Consistent Identification

Level AA

Components that have the same functionality within a set of Web pages are identified consistently.

Understanding Consistent Identification
How to Meet Consistent Identification

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3.2.5 Change on Request

Level AAA

Changes of context are initiated only by user request or a mechanism is available to turn off such changes.

Understanding Change on Request
How to Meet Change on Request

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Guideline 3.3 Input Assistance

Help users avoid and correct mistakes.

3.3.1 Error Identification

Level A

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.

Understanding Error Identification
How to Meet Error Identification

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3.3.2 Labels or Instructions

Level A

Labels or instructions are provided when content requires user input.

Understanding Labels or instructions
How to Meet Labels or instructions

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3.3.3 Error Suggestion

Level AA

If an input error is automatically detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content.

Understanding Error Suggestion
How to Meet Error Suggestion

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3.3.4 Error Prevention (Legal, Financial, Data)

Level AA

For Web pages that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true:

Understanding Error Prevention (legal, financial, data)
How to Meet Error Prevention (legal, financial, data)

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3.3.5 Help

Level AAA

Context-sensitive help is available.

Understanding Help
How to Meet Help 

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3.3.6 Error Prevention (All)

Level AAA

For Web pages that require the user to submit information, at least one of the following is true:

Understanding Error Prevention (All)
How to Meet Error Prevention (All)

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Principle 4. Robust

Content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies.

Guideline 4.1 Compatible

Maximize compatibility with current and future user agents, including assistive technologies.

4.1.1 Parsing

Level A

In content die geïmplementeerd is met opmaaktalen hebben elementen volledige begin- en eindtags, zijn elementen genest volgens hun specificatie, bevatten elementen geen dubbele attributen en zijn alle ID’s uniek, behalve waar de specificatie deze eigenschappen toelaat.

Understanding Parsing
How to Meet Parsing

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4.1.2 Name, Role, Value

Level A

For all user interface components (including but not limited to: form elements, links and components generated by scripts), 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.

Understanding Name, Role, Value
How to Meet Name, Role, Value

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4.1.3 Status Messages

Level AA

In content implemented using markup languages, status messages can be programmatically determined through role or properties such that they can be presented to the user by assistive technologies without receiving focus.

Understanding Status Messages
How to Meet Status Messages

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Glossary

This paragraph is normative.

abbreviation

shortened form of a word, phrase, or name where the abbreviation has not become part of the language.

Note: This includes initialisms and acronyms where:

• initialisms are shortened forms of a name or phrase made from the initial letters of words or syllables contained in that name or phrase. Note 1: Not defined in all languages. Example 1: SNCF is een Frans letterwoord dat de beginletters bevat van de Société Nationale des Chemins de Fer, de Franse nationale spoorwegen. Example 2: ESP is an initialism for extrasensory perception.
• acronyms are abbreviated forms made from the initial letters or parts of other words (in a name or phrase) which may be pronounced as a word. Example: NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States.

Note 2: Some companies have adopted what used to be an initialism as their company name. In these cases, the new name of the company is the letters (for example, Ecma) and the word is no longer considered an abbreviation.

accessibility supported

supported by users’ assistive technologies as well as the accessibility features in browsers and other user agents

To qualify as an accessibility-supported use of a Web content technology (or feature of a technology), both 1 and 2 must be satisfied for a Web content technology (or feature):

1. The way that the Web content technology is used must be supported by users’ assistive technology (AT). This means that the way that the technology is used has been tested for interoperability with users’ assistive technology in the human language(s) of the content, AND
2. The Web content technology must have accessibility-supported user agents that are available to users. This means that at least one of the following four statements is true:
   1. The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS); OR
   2. The technology is supported in a widely-distributed plug-in that is also accessibility supported; OR
   3. The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported; OR
   4. The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that:
      • does not cost a person with a disability any more than a person without a disability and
      • is as easy to find and obtain for a person with a disability as it is for a person without disabilities.

Note 1: The Accessibility Guidelines Working Group and the W3C do not specify which or how much support by assistive technologies there must be for a particular use of a Web technology in order for it to be classified as accessibility supported. (See Level of Assistive Technology Support Needed for “Accessibility Support”.)

Note 2: Web technologies can be used in ways that are not accessibility supported as long as they are not relied upon and the page as a whole meets the conformance requirements, including Conformance Requirement 4 and Conformance Requirement 5.

Note 3: When a Web Technology is used in a way that is “accessibility supported,” it does not imply that the entire technology or all uses of the technology are supported. Most technologies, including HTML, lack support for at least one feature or use. Pages conform to WCAG only if the uses of the technology that are accessibility supported can be relied upon to meet WCAG requirements.

Note 4: When citing Web content technologies that have multiple versions, the version(s) supported should be specified.

Note 5: One way for authors to locate uses of a technology that are accessibility supported would be to consult compilations of uses that are documented to be accessibility supported. (See Understanding Accessibility-Supported Web Technology Uses.) Authors, companies, technology vendors, or others may document accessibility-supported ways of using Web content technologies. However, all ways of using technologies in the documentation would need to meet the definition of accessibility-supported Web content technologies above.

alternative for time-based media

document including correctly sequenced text descriptions of time-based visual and auditory information and providing a means for achieving the outcomes of any time-based interaction

Note: A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing.

ambiguous to users in general

the purpose cannot be determined from the link and all information of the Web page presented to the user simultaneously with the link (i.e., readers without disabilities would not know what a link would do until they activated it)

Example: The word guava in the following sentence “One of the notable exports is guava” is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage.

ASCII-art

picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII)

assistive technology (as used in this document)

hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide functionality to meet the requirements of users with disabilities that go beyond those offered by mainstream user agents

Note 1: functionality provided by assistive technology includes alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible).

Note 2: Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs.

Note 3: The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.

Example: Assistive technologies that are important in the context of this document include the following:

• screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc. in order to improve the visual readability of rendered text and images;
• screen readers, which are used by people who are blind to read textual information through synthesized speech or braille;
• text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech;
• speech recognition software, which may be used by people who have some physical disabilities;
• alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard (including alternate keyboards that use head pointers, single switches, sip/puff and other special input devices.);
• alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.

audio

the technology of sound reproduction

Note: Audio can be created synthetically (including speech synthesis), recorded from real world sounds, or both.

audio description

narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone

Note 1: Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content.

Note 2: In standard audio description, narration is added during existing pauses in dialogue. (See also extended audio description.)

Note 3: Where all of the video information is already provided in existing audio, no additional audio description is necessary.

Note 4: Also called “video description” and “descriptive narration.”

audio-only

a time-based presentation that contains only audio (no video and no interaction)

blinking

switch back and forth between two visual states in a way that is meant to draw attention

Note: See also flash. It is possible for something to be large enough and blink brightly enough at the right frequency to be also classified as a flash.

blocks of text

more than one sentence of text

CAPTCHA

initialism for “Completely Automated Public Turing test to tell Computers and Humans Apart”

Note 1: CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file

Note 2: A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University.

captions

synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content

Note 1: Captions are similar to dialogue-only subtitles except captions convey not only the content of spoken dialogue, but also equivalents for non-dialogue audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location.

Note 2: Closed Captions are equivalents that can be turned on and off with some players.

Note 3: Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent images of text embedded in video.

Note 4: Captions should not obscure or obstruct relevant information in the video.

Note 5: In some countries, captions are called subtitles.

Note 6: Audio descriptions can be, but do not need to be, captioned since they are descriptions of information that is already presented visually.

changes of context

major changes that, if made without user awareness, can disorient users who are not able to view the entire page simultaneously

Veranderingen in context zijn onder meer veranderingen van:

• user agent;
• view
• port;
• focus;
• content that changes the meaning of the Web page.

Note: A change of content is not always a change of context. Changes in content, such as an expanding outline, dynamic menu, or a tab control do not necessarily change the context, unless they also change one of the above (e.g., focus).

Example: Opening a new window, moving focus to a different component, going to a new page (including anything that would look to a user as if they had moved to a new page) or significantly re-arranging the content of a page are examples of changes of context.

conformance

satisfying all the requirements of a given standard, guideline or specification

conforming alternate version

version that

1. conforms at the designated level, and
2. provides all of the same information and functionality in the same human language, and
3. is as up to date as the non-conforming content, and
4. for which at least one of the following is true:
   1. the conforming version can be reached from the non-conforming page via an accessibility-supported mechanism, or
   2. the non-conforming version can only be reached from the conforming version, or
   3. the non-conforming version can only be reached from a conforming page that also provides a mechanism to reach the conforming version

Note 1: In this definition, “can only be reached” means that there is some mechanism, such as a conditional redirect, that prevents a user from “reaching” (loading) the non-conforming page unless the user had just come from the conforming version.

Note 2: The alternate version does not need to be matched page for page with the original (e.g., the conforming alternate version may consist of multiple pages).

Note 3: If multiple language versions are available, then conforming alternate versions are required for each language offered.

Note 4: Alternate versions may be provided to accommodate different technology environments or user groups. Each version should be as conformant as possible. One version would need to be fully conformant in order to meet conformance requirement 1.

Note 5: The conforming alternative version does not need to reside within the scope of conformance, or even on the same Web site, as long as it is as freely available as the non-conforming version.

Note 6: Alternate versions should not be confused with supplementary content, which support the original page and enhance comprehension.

Note 7: Setting user preferences within the content to produce a conforming version is an acceptable mechanism for reaching another version as long as the method used to set the preferences is accessibility supported.

See Understanding Conforming Alternate Versions.

content (Web content)

information and sensory experience to be communicated to the user by means of a user agent, including code or markup that defines the content’s structure, presentation, and interactions

context sensitive help

help text that provides information related to the function currently being performed

Note: Clear labels can act as context-sensitive help.

contrast ratio

(L1 + 0,05) / (L2 + 0,05), where

• L1 is the relative luminance of the lighter of the colors, and
• L2 it the relative luminance of the darker of the colors.

Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).

Note 2: Because authors do not have control over user settings as to how text is rendered (for example font smoothing or anti-aliasing), the contrast ratio for text can be evaluated with anti-aliasing turned off.

Note 3: For the purpose of Success Criteria 1.4.3 and 1.4.6, contrast is measured with respect to the specified background over which the text is rendered in normal usage. If no background color is specified, then white is assumed.

Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. It is a failure if no background color is specified when the text color is specified, because the user’s default background color is unknown and cannot be evaluated for sufficient contrast. For the same reason, it is a failure if no text color is specified when a background color is specified.

Note 5: When there is a border around the letter, the border can add contrast and would be used in calculating the contrast between the letter and its background. A narrow border around the letter would be used as the letter. A wide border around the letter that fills in the inner details of the letters acts as a halo and would be considered background.

Note 6: WCAG conformance should be evaluated for color pairs specified in the content that an author would expect to appear adjacent in typical presentation. Authors need not consider unusual presentations, such as color changes made by the user agent, except where caused by authors’ code.

correct reading sequence

any sequence where words and paragraphs are presented in an order that does not change the meaning of the content

CSS-pixel

visual angle of about 0.0213 degrees

A CSS pixel is the canonical unit of measure for all lengths and measurements in CSS. This unit is density-independent, and distinct from actual hardware pixels present in a display. User agents and operating systems should ensure that a CSS pixel is set as closely as possible to the CSS Values and Units Module Level 3 reference pixel [css3-values], which takes into account the physical dimensions of the display and the assumed viewing distance (factors that cannot be determined by content authors).

down-event

platform event that occurs when the trigger stimulus of a pointer is depressed

The down-event may have different names on different platforms, such as “touchstart” or “mousedown”.

emergency

a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property

essential

if removed, would fundamentally change the information or functionality of the content, and information and functionality cannot be achieved in another way that would conform

extended audio description

audio description that is added to an audiovisual presentation by pausing the video so that there is time to add additional description

Note: This technique is only used when the sense of the video would be lost without the additional audio description and the pauses between dialogue/narration are too short.

flash

a pair of opposing changes in relative luminance that can cause seizures in some people if it is large enough and in the right frequency range

Note 1: See general flash and red flash thresholds for information about types of flash that are not allowed.

Note 2: See also blinking.

functionality

processes and outcomes achievable through user action

general flash and red flash thresholds

a flash or rapidly changing image sequence is below the threshold (i.e., content passes) if any of the following are true:

1. there are no more than three general flashes and / or no more than three red flashes within any one-second period; or
2. the combined area of flashes occurring concurrently occupies no more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance where:

• A general flash is defined as a pair of opposing changes in relative luminance of 10% or more of the maximum relative luminance (1.0) where the relative luminance of the darker image is below 0.80; and where “a pair of opposing changes” is an increase followed by a decrease, or a decrease followed by an increase, and
• A general flash is defined as a pair of opposing changes in relative luminance of 10% or more of the maximum relative luminance (1.0) where the relative luminance of the darker image is below 0.80; and where “a pair of opposing changes” is an increase followed by a decrease, or a decrease followed by an increase, and

Exception: Flashing that is a fine, balanced, pattern such as white noise or an alternating checkerboard pattern with “squares” smaller than 0.1 degree (of visual field at typical viewing distance) on a side does not violate the thresholds.

Note 1: For general software or Web content, using a 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels will provide a good estimate of a 10 degree visual field for standard screen sizes and viewing distances (e.g., 15-17 inch screen at 22-26 inches). This resolution of 75 – 85 ppi is known to be lower, and thus more conservative than the nominal CSS pixel resolution of 96 ppi in CSS specifications. Higher resolutions displays showing the same rendering of the content yield smaller and safer images so it is lower resolutions that are used to define the thresholds.

Note 2: A transition is the change in relative luminance (or relative luminance/color for red flashing) between adjacent peaks and valleys in a plot of relative luminance (or relative luminance/color for red flashing) measurement against time. A flash consists of two opposing transitions.

Note 3: The new working definition in the field for “pair of opposing transitions involving a saturated red” (from WCAG 2.2) is a pair of opposing transitions where, one transition is either to or from a state with a value R/(R + G + B) that is greater than or equal to 0.8, and the difference between states is more than 0.2 (unitless) in the CIE 1976 UCS chromaticity diagram. [ISO_9241-391]

Note 4: Tools are available that will carry out analysis from video screen capture. However, no tool is necessary to evaluate for this condition if flashing is less than or equal to 3 flashes in any one second. Content automatically passes (see #1 and #2 above).

human language

language that is spoken, written or signed (through visual or tactile means) to communicate with humans

Note: See also sign language.

idiom

phrase whose meaning cannot be deduced from the meaning of the individual words and the specific words cannot be changed without losing the meaning

Note: idioms cannot be translated directly, word for word, without losing their (cultural or language-dependent) meaning.

Example 1: In English, “spilling the beans” means “revealing a secret.” However, “knocking over the beans” or “spilling the vegetables” does not mean the same thing.

Example 2: In Japanese, the phrase ” さじをæげる” literally translates into “he throws a spoon,” but it means that there is nothing he can do and finally he gives up.

Example 3: In Dutch, “Hij ging met de kippen op stok” literally translates into “He went to roost with the chickens,” but it means that he went to bed early.

image of text

text that has been rendered in a non-text form (e.g., an image) in order to achieve a particular visual effect

Note: This does not include text that is part of a picture that contains significant other visual content.

Example: A person’s name on a nametag in a photograph.

informative

for information purposes and not required for conformance

Note: Content required for conformance is referred to as “normative.”

input error

information provided by the user that is not accepted

Note:

This includes:

1. Information that is required by the Web page but omitted by the user
2. Information that is provided by the user but that falls outside the required data format or values

jargon

words used in a particular way by people in a particular field

Example: The word StickyKeys is jargon from the field of assistive technology/accessibility.

keyboard interface

interface used by software to obtain keystroke input

Note: A keyboard interface allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.

Example: A touchscreen PDA has a keyboard interface built into its operating system as well as a connector for external keyboards. Applications on the PDA can use the interface to obtain keyboard input either from an external keyboard or from other applications that provide simulated keyboard output, such as handwriting interpreters or speech-to-text applications with “keyboard emulation” functionality.

Note 2: Operation of the application (or parts of the application) through a keyboard-operated mouse emulator, such as MouseKeys, does not qualify as operation through a keyboard interface because operation of the program is through its pointing device interface, not through its keyboard interface.

keyboard shortcut

alternative means of triggering an action by the pressing of one or more keys

label

text or other component with a text alternative that is presented to a user to identify a component within Web content

Note 1: A label is presented to all users whereas the name may be hidden and only exposed by assistive technology. In many (but not all) cases the name and the label are the same.

Note 2: The term label is not limited to the label element in HTML.

large scale (text)

with at least 18 point or 14 point bold or font size that would yield equivalent size for Chinese, Japanese and Korean (CJK) fonts

Note 1: Fonts with extraordinarily thin strokes or unusual features and characteristics that reduce the familiarity of their letter forms are harder to read, especially at lower contrast levels.

Note 2: Font size is the size when the content is delivered. It does not include resizing that may be done by a user.

Note 3: The actual size of the character that a user sees is dependent both on the author-defined size and the user’s display or user agent settings. For many mainstream body text fonts, 14 and 18 point is roughly equivalent to 1.2 and 1.5 em or to 120% or 150% of the default size for body text (assuming that the body font is 100%), but authors would need to check this for the particular fonts in use. When fonts are defined in relative units, the actual point size is calculated by the user agent for display. The point size should be obtained from the user agent, or calculated based on font metrics as the user agent does, when evaluating this success criterion. Users who have low vision would be responsible for choosing appropriate settings.

Note 4: When using text without specifying the font size, the smallest font size used on major browsers for unspecified text would be a reasonable size to assume for the font. If a level 1 heading is rendered in 14pt bold or higher on major browsers, then it would be reasonable to assume it is large text. Relative scaling can be calculated from the default sizes in a similar fashion.

Note 5: The 18 and 14 point sizes for roman texts are taken from the minimum size for large print (14pt) and the larger standard font size (18pt). For other fonts such as CJK languages, the “equivalent” sizes would be the minimum large print size used for those languages and the next larger standard large print size.

legal commitments

transactions where the person incurs a legally binding obligation or benefit

Example: A marriage license, a stock trade (financial and legal), a will, a loan, adoption, signing up for the army, a contract of any type, etc.

link purpose

nature of the result obtained by activating a hyperlink

live

information captured from a real-world event and transmitted to the receiver with no more than a broadcast delay

Note 1: A broadcast delay is a short (usually automated) delay, for example used in order to give the broadcaster time to cue or censor the audio (or video) feed, but not sufficient to allow significant editing.

Note 2: If information is completely computer generated, it is not live.

lower secondary education level

the two or three year period of education that begins after completion of six years of school and ends nine years after the beginning of primary education

Note: This definition is based on the International Standard Classification of Education [UNESCO].

mechanism

process or technique for achieving a result

Note 1: The mechanism may be explicitly provided in the content, or may be relied upon to be provided by either the platform or by user agents, including assistive technologies.

Note 2: The mechanism needs to meet all success criteria for the conformance level claimed.

media-alternative for text

media that presents no more information than is already presented in text (directly or via text alternatives)

Note: A media alternative for text is provided for those who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.

motion animation

addition of steps between conditions to create the illusion of movement or to give a sense of a smooth transition

Example: For example, an element which moves into place or changes size while appearing is considered to be animated. An element which appears instantly without transitioning is not using animation. Motion animation does not include changes of color, blurring, or opacity which do not change the perceived size, shape, or position of the element.

name

text by which software can identify a component within Web content to the user

Note 1: The name may be hidden and only exposed by assistive technology, whereas a label is presented to all users. In many (but not all) cases, the label and the name are the same.

Note 2: This is unrelated to the name attribute in HTML.

navigated sequentially

navigated in the order defined for advancing focus (from one element to the next) using a keyboard interface

non-text content

any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language

Note: This includes ASCII Art (which is a pattern of characters), emoticons, leetspeak (which uses character substitution), and images representing text

normative

required for conformance

Note 1: One may conform in a variety of well-defined ways to this document.

Note 2: Content identified as “informative” or “non-normative” is never required for conformance.

on a full-screen window

on the most common sized desktop/laptop display with the viewport maximized

Note: Since people generally keep their computers for several years, it is best not to rely on the latest desktop/laptop display resolutions but to consider the common desktop/laptop display resolutions over the course of several years when making this evaluation.

paused

stopped by user request and not resumed until requested by user

pointer input

input from a device that can target a specific coordinate (or set of coordinates) on a screen, such as a mouse, pen, or touch contact

Note: See the Pointer Events definition for “pointer”

prerecorded

information that is not live

presentation

rendering of the content in a form to be perceived by users

primary education level

six year time period that begins between the ages of five and seven, possibly without any previous education

Note: This definition is based on the International Standard Classification of Education [UNESCO].

process

series of user actions where each action is required in order to complete an activity

Example 1: Successful use of a series of Web pages on a shopping site requires users to view alternative products, prices and offers, select products, submit an order, provide shipping information and provide payment information.

Example 2: An account registration page requires successful completion of a Turing test before the registration form can be accessed.

programmatically determined (programmatically determinable)

determined by software from author-supplied data provided in a way that different user agents, including assistive technologies, can extract and present this information to users in different modalities

Example 1: Determined in a markup language from elements and attributes that are accessed directly by commonly available assistive technology.

Example 2: Determined from technology-specific data structures in a non-markup language and exposed to assistive technology via an accessibility API that is supported by commonly available assistive technology.

programmatically determined link context

additional information that can be programmatically determined from relationships with a link, combined with the link text, and presented to users in different modalities

Example: In HTML, information that is programmatically determinable from a link in English includes text that is in the same paragraph, list, or table cell as the link or in a table header cell that is associated with the table cell that contains the link.

Note: Since screen readers interpret punctuation, they can also provide the context from the current sentence, when the focus is on a link in that sentence.

programmatically set

set by software using methods that are supported by user agents, including assistive technologies

pure decoration

serving only an aesthetic purpose, providing no information, and having no functionality

Note: Text is only purely decorative if the words can be rearranged or substituted without changing their purpose

Example: The cover page of a dictionary has random words in very light text in the background.

real-time event

event that a) occurs at the same time as the viewing and b) is not completely generated by the content

Example 1: A Webcast of a live performance (occurs at the same time as the viewing and is not prerecorded).

Example 2: An on-line auction with people bidding (occurs at the same time as the viewing).

Example 3: Live humans interacting in a virtual world using avatars (is not completely generated by the content and occurs at the same time as the viewing).

region

perceivable, programmatically determined section of content

Note: In HTML, any area designated with a landmark role would be a region.

relationships

meaningful associations between distinct pieces of content

relative luminance

the relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white

Note 1: For the sRGB colorspace, the relative luminance of a color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R, G and B are defined as:

• if RsRGB <= 0.04045 then R = RsRGB/12.92 else R = ((RsRGB+0.055)/1.055) ^ 2.4
• if GsRGB <= 0.04045 then G = GsRGB/12.92 else G = ((GsRGB+0.055)/1.055) ^ 2.4
• if BsRGB <= 0.04045 then B = BsRGB/12.92 else B = ((BsRGB+0.055)/1.055) ^ 2.4

and RsRGB, GsRGB, and BsRGB are defined as:

• RsRGB = R8bit/255
• GsRGB = G8bit/255
• BsRGB = B8bit/255

The “^” character is the exponentiation operator. (Formula taken from [SRGB].)

Note 2: Before May 2021 the value of 0.04045 in the definition was different (0.03928). It was taken from an older version of the specification and has been updated. It has no practical effect on the calculations in the context of these guidelines.

Note 3: Almost all systems used today to view Web content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see Understanding Success Criterion 1.4.3.

Note 4: If dithering occurs after delivery, then the source color value is used. For colors that are dithered at the source, the average values of the colors that are dithered should be used (average R, average G, and average B).

Note 5: Tools are available that automatically do the calculations when testing contrast and flash.

Note 6: A separate page giving the relative luminance definition using MathML to display the formulas is available.

relied upon (technologies that are)

the content would not conform if that technology is turned off or is not supported

role

text or number by which software can identify the function of a component within Web content

Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.

same functionality

same result when used

Example: A submit “search” button on one Web page and a “find” button on another Web page may both have a field to enter a term and list topics in the Web site related to the term submitted. In this case, they would have the same functionality but would not be labeled consistently.

same relative order

same position relative to other items

Note: Items are considered to be in the same relative order even if other items are inserted or removed from the original order. For example, expanding navigation menus may insert an additional level of detail or a secondary navigation section may be inserted into the reading order.

satisfies a succes criterion

the success criterion does not evaluate to ‘false’ when applied to the page

section

a self-contained portion of written content that deals with one or more related topics or thoughts

Note: A section may consist of one or more paragraphs and include graphics, tables, lists and sub-sections.

set of web pages

collection of web pages that share a common purpose and that are created by the same author, group or organization

Example: Examples include:

• a publication which is split across multiple Web pages, where each page contains one chapter or other significant section of the work. The publication is logically a single contiguous unit, and contains navigation features that enable access to the full set of pages.
• an e-commerce website shows products in a set of Web pages that all share the same navigation and identification. However, when progressing to the checkout process, the template changes; the navigation and other elements are removed, so the pages in that process are functionally and visually different. The checkout pages are not part of the set of product pages.
• a blog on a sub-domain (e.g. blog.example.com) which has a different navigation and is authored by a distinct set of people from the pages on the primary domain (example.com).

Note: Different language versions would be considered different sets of Web pages.

sign language

a language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning

sign language interpretation

translation of one language, generally a spoken language, into a sign language

Note: True sign languages are independent languages that are unrelated to the spoken language(s) of the same country or region.

single pointer

pointer input that operates with one point of contact with the screen, including single taps and clicks, double-taps and clicks, long presses, and path-based gestures.

specific sensory experience

a sensory experience that is not purely decorative and does not primarily convey important information or perform a function

Example: Examples include a performance of a flute solo, works of visual art etc.

state

dynamic property expressing characteristics of a user interface component that may change in response to user action or automated processes

States do not affect the nature of the component, but represent data associated with the component or user interaction possibilities. Examples include focus, hover, select, press, check, visited/unvisited, and expand/collapse.

status message

change in content that is not a change of context, and that provides information to the user on the success or results of an action, on the waiting state of an application, on the progress of a process, or on the existence of errors.

structure

1. The way the parts of a Web page are organized in relation to each other; and
2. The way a collection of Web pages is organized.

style property

property whose value determines the presentation (e.g. font, color, size, location, padding, volume, synthesized speech prosody) of content elements as they are rendered (e.g. onscreen, via loudspeaker, via braille display) by user agents

Style properties can have several origins:

• User agent default styles: The default style property values applied in the absence of any author or user styles. Some web content technologies specify a default rendering, others do not;
• Author styles: Style property values that are set by the author as part of the content (e.g. in-line styles, author style sheets);
• User styles: Style property values that are set by the user (e.g. via user agent interface settings, user style sheets)

supplementary content

additional content that illustrates or clarifies the primary content

Example 1: An audio version of a Web page.

Example 2: An illustration of a complex process.

Example 3: A paragraph summarizing the major outcomes and recommendations made in a research study.

synchronized media

audio or video synchronized with another format for presenting information and/or with time-based interactive components, unless the media is a media alternative for text that is clearly labeled as such

target

region of the display that will accept a pointer action, such as the interactive area of a user interface component

Wanneer er sprake is van overlapping tussen twee of meer doelgebieden voor aanraken (touch), dan moet het overlappende gedeelte niet worden meegenomen bij het berekenen van de grootte van het doel, tenzij de overlappende doelen dezelfde actie uitvoeren of dezelfde pagina openen.

technology (web content)

mechanism for encoding instructions to be rendered, played or executed by user agents

Note 1: As used in these guidelines “Web Technology” and the word “technology” (when used alone) both refer to Web Content Technologies.

Note 2: Web content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static Web pages to synchronized media presentations to dynamic Web applications.

Example: Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.

text

sequence of characters that can be programmatically determined, where the sequence is expressing something in human language

text alternative

Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. Programmatically associated text is text whose location can be programmatically determined from the non-text content.

Example: An image of a chart is described in text in the paragraph after the chart. The short text alternative for the chart indicates that a description follows.

Note: Refer to Understanding Text Alternatives for more information.

up-event

platform event that occurs when the trigger stimulus of a pointer is released

The up-event may have different names on different platforms, such as “touchend” or “mouseup”.

used in an unusual or restricted way

words used in such a way that requires users to know exactly which definition to apply in order to understand the content correctly

Example: The term “gig” means something different if it occurs in a discussion of music concerts than it does in article about computer hard drive space, but the appropriate definition can be determined from context. By contrast, the word “text” is used in a very specific way in WCAG 2.1, so a definition is supplied in the glossary.

user agent

any software that retrieves and presents Web content for users

Example: Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving, rendering, and interacting with Web content.

user-controllable

data that is intended to be accessed by users

Note: This does not refer to such things as Internet logs and search engine monitoring data.

Example: Name and address fields for a user’s account.

user inactivity

any continuous period of time where no user actions occur

The method of tracking will be determined by the web site or application.

user interface component

a part of the content that is perceived by users as a single control for a distinct function

Note 1: Multiple user interface components may be implemented as a single programmatic element. “Components” here is not tied to programming techniques, but rather to what the user perceives as separate controls.

Note 2: User interface components include form elements and links as well as components generated by scripts.

Note 3: What is meant by “component” or “user interface component” here is also sometimes called “user interface element”.

video

the technology of moving or sequenced pictures or images

Note: Video can be made up of animated or photographic images, or both.

video-only

a time-based presentation that contains only video (no audio and no interaction)

viewport

object in which the user agent presents content

Note 1: The user agent presents content through one or more viewports. Viewports include windows, frames, loudspeakers, and virtual magnifying glasses. A viewport may contain another viewport (e.g., nested frames). Interface components created by the user agent such as prompts, menus, and alerts are not viewports.

Note 2: For the purposes of conformance with these guidelines, a resource must be “non-embedded” within the scope of conformance to be considered a Web page.

visually customized

the font, size, color, and background can be set

web page

a non-embedded resource obtained from a single URI using HTTP plus any other resources that are used in the rendering or intended to be rendered together with it by a user agent

Note 1: Although any “other resources” would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.

Note 2: For the purposes of conformance with these guidelines, a resource must be “non-embedded” within the scope of conformance to be considered a Web page.

Example 1: A web resource including all embedded images and media.

Example 2: A web mail program built using Asynchronous JavaScript and XML (AJAX). The program lives entirely at http://example.com/mail, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause the inbox, contacts, or calendar to display, but do not change the URI of the page as a whole.

Example 3: A customizable portal site, where users can choose content to display from a set of different content modules.

Example 4: When you enter “http://shopping.example.com/” in your browser, you enter a movie-like interactive shopping environment where you visually move around in a store dragging products off of the shelves around you and into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside. This might be a single-page Web site or just one page within a Web site.

Input Purposes for User Interface Components

This section contains a listing of common user interface component input purposes. The terms below are not keywords that must be used, but instead represent purposes that must be captured in the taxonomy adopted by a webpage. Where applicable, authors mark up controls with the chosen taxonomy to indicate the semantic purpose. This provides the potential for user agents and assistive technologies to apply personalized presentations that can enable more people to understand and use the content.

The following input control purposes are intended to relate to the user of the content and pertain only to information related to that individual.

References

Normative references

[css3-values]
CSS Values and Units Module Level 3. Tab Atkins Jr.; Elika Etemad. W3C. 29 September 2016. W3C Candidate Recommendation. URL: https://www.w3.org/TR/css-values-3/

[pointerevents]
Pointer Events. Jacob Rossi; Matt Brubeck. W3C. 24 February 2015. W3C Recommendation. URL: https://www.w3.org/TR/pointerevents/

[WCAG20]
Web Content Accessibility Guidelines (WCAG) 2.0. Ben Caldwell; Michael Cooper; Loretta Guarino Reid; Gregg Vanderheiden et al. W3C. 11 December 2008. W3C Recommendation. URL: https://www.w3.org/TR/WCAG20/

Informative references

[HARDING-BINNIE]
Independent Analysis of the ITC Photosensitive Epilepsy Calibration Test Tape. Harding G. F. A.; Binnie, C.D..2002.

[IEC-4WD]
IEC/4WD 61966-2-1: Colour Measurement and Management in Multimedia Systems and Equipment – Part 2.1: Default Colour Space – sRGB. May 5, 1998.

[RFC2119]
Key words for use in RFCs to Indicate Requirement Levels . S. Bradner. IETF. March 1997. Best Current Practice. URL: https://tools.ietf.org/html/rfc2119

[sRGB]
A Standard Default Color Space for the Internet – sRGB, Version 1.10. M. Stokes; M. Anderson; S. Chandrasekar; R. Motta.November 5, 1996. URL: https://www.w3.org/Graphics/Color/sRGB.html

[UAAG10]
User Agent Accessibility Guidelines 1.0. Ian Jacobs; Jon Gunderson; Eric Hansen. W3C. 17 December 2002. W3C Recommendation. URL: https://www.w3.org/TR/UAAG10/

[UNESCO]
International Standard Classification of Education. 1997. URL: http://uis.unesco.org/sites/default/files/documents/international-standard-classification-of-education-1997-en_0.pdf

[WAI-WEBCONTENT]
Web Content Accessibility Guidelines 1.0. Wendy Chisholm; Gregg Vanderheiden; Ian Jacobs. W3C. 5 May 1999. W3C Recommendation. URL: https://www.w3.org/TR/WAI-WEBCONTENT/