Understanding accessibility principles - Operable
There are four principles in the Web Content Accessibility Guidelines (WCAG) which lay the foundation for anyone accessing and using web content. In this edition we provide specific details and examples about the second principle, Operable. This principle ensures that users can navigate the web page using a keyboard only.
Make all functionality available from a keyboard
The intent of this criterion is to ensure that the content does not 'trap' keyboard focus within subsections of content on a web page. All functionality of the content can be operated using a keyboard without requiring specific timings for individual keystrokes.
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.
Note: Since any content that does not meet this 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 criteria or not) must meet this criterion.
Provide users with enough time to read and use content
People with disabilities such as blindness, low vision, dexterity impairments, and cognitive limitations may require more time to read content or to perform functions such as filling out on-line forms. If web functions are time-dependent, it will be difficult for some users to perform the required action before a time limit occurs. Providing options to disable time limits, customise the length of time limits, or request more time before a time limit occurs helps those users who require more time than expected to successfully complete tasks.
Pause, stop, hide
For moving, blinking, scrolling, or auto-updating information, ALL of the following criteria must be met:
- Moving, blinking, scrolling: For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than five seconds, 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; and
- Auto-updating: For any auto-updating information that (1) starts automatically and (2) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it or to control the frequency of the update unless the auto-updating is part of an activity where it is essential.
Design content in a way that is known not to cause seizures
Web pages should 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.
Content that does not meet this criterion can interfere with a user's ability to use the whole page.
Provide ways to help users navigate, find content, and determine where they are
The intent of this criterion is to help users find the content they need and allow them to keep track of their location. These tasks are often more difficult for people with disabilities. For finding, navigation, and orientation, it is important that the user can find out what the current location is. For navigation, information about the possible destinations needs to be available. Screen readers convert content to synthetic speech which, because it is audio, must be presented in linear order. Some Success Criteria in this guideline explain what provisions need to be taken to ensure that screen reader users can successfully navigate the content. Others allow users to more easily recognise navigation bars and page headers and to bypass this repeated content. Unusual user interface features or behaviours may confuse people with cognitive disabilities.
Bypass blocks: A mechanism is available to bypass blocks of content that are repeated on multiple web pages. (eg 'Skip to content')
Page titled: Web pages have titles that describe topic or purpose.
Focus order: 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.
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.
Multiple ways: 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.
Headings and labels: Headings and labels describe topic or purpose.
Focus visible: Any keyboard operable user interface has a mode of operation where the keyboard focus indicator is visible.