WCAG

Below are some principles that apply more directly to UI and UX.

W3 Website

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.

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:

• Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;

• Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.

• Logotypes: Text that is part of a logo or brand name has no contrast requirement.

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.

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:

• Customizable: The image of text can be visually customized to the user's requirements

• Essential: A particular presentation of text is essential to the information being conveyed.
  

Note 1: Logotypes (text that is part of a logo or brand name) are considered essential.

1.4.8 Visual Presentation – Level AAA

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

• Foreground and background colors can be selected by the user.

• Width is no more than 80 characters or glyphs (40 if CJK).
  

• Text is not justified (aligned to both the left and the right margins).
  

• Line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing.
  

• Text can be resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text on a full-screen window.
  

1.4.10 Reflow – Level AA

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

• Vertical scrolling content at a width equivalent to 320 CSS pixels

• Horizontal scrolling content at a height equivalent to 256 CSS pixels
  

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

1.4.11 Non-text Contrast – Level 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.
  

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:

• Line height (line spacing) to at least 1.5 times the font size

• Spacing following paragraphs to at least 2 times the font size
  

• Letter spacing (tracking) to at least 0.12 times the font size
  

• Word spacing to at least 0.16 times the font size
  

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.

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:

• Dismissible: A mechanism is available to dismiss the additional content without moving pointer hover or keyboard focus, unless the additional content communicates an input error or does not obscure or replace other content

• Hoverable: If pointer hover can trigger the additional content, then the pointer can be moved over the additional content without the additional content disappearing
  

• Persistent: The additional content remains visible until the hover or focus trigger is removed, the user dismisses it, or its information is no longer valid.
  

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

1.4.11 Non-text Contrast – Level AA

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

Guideline 2.2 – Enough Time

Provide users enough time to read and use content.

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.

2.2.4 Interruptions – Level AAA

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

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.

• Note 1: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.
  

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.

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.

2.4.2 Page Titled – Level A

Web pages have titles that describe topic or purpose.

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.

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.

2.4.6 Headings and Labels – Level AA

Headings and labels describe topic or purpose.

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.

2.4.10 Section Headings – Level AAA

Section headings are used to organize the content.

• Note 1: "Heading" is used in its general sense and includes titles and other ways to add a heading to different types of content.
  

• Note 2: This success criterion covers sections within writing, not user interface components. User Interface components are covered under Success Criterion 4.1.2.
  

Guideline 2.5 – Input Modalities

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

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:

• Equivalent: The target is available through an equivalent link or control on the same page that is at least 44 by 44 CSS pixels
  

• Inline: The target is in a sentence or block of text;
  

• User Agent Control: The size of the target is determined by the user agent and is not modified by the author
  

• Essential: A particular presentation of the target is essential to the information being conveyed.
  

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.

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.

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.

3.2.4 Consistent Identification – Level AA

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

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.

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.

3.3.2 Labels or Instructions – Level A

Labels or instructions are provided when content requires user input.

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.