Understanding accessibility principles - Understandable

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 third principle, Understandable.

Text is readable and understandable

Content authors need to ensure that text content is readable and understandable to the broadest audience possible, including when it is read aloud by text-to-speech. This includes:

  • Identifying the primary language of a web page, such as Arabic, Dutch, or Korean
  • Identifying the language of text passages, phrases, or other parts of a web page
  • Providing definitions for any unusual words, phrases, idioms, and abbreviations
  • Using the clearest and simplest language possible, or providing simplified versions.

Meeting this requirement helps software, including assistive technology, to process text content correctly. For instance, this requirement helps software to read the content aloud, to generate page summaries, and to provide definitions for unusual words such as technical jargon. It also helps people who have difficulty understanding more complex sentences, phrases, and vocabulary. In particular, it helps people with different types of cognitive disabilities.

Content appears and operates in predictable ways

Many people rely on predictable user interfaces and are disoriented or distracted by inconsistent appearance or behaviour. Examples of making content more predictable include:

  • Navigation mechanisms that are repeated on multiple pages appear in the same place each time
  • User interface components that are repeated on web pages have the same labelling each time
  • Significant changes on a web page do not happen without the consent of the user

Meeting this requirement helps people to quickly learn the functionality and navigation mechanisms provided on a website, and to operate them according to their specific needs and preferences. For instance, some people assign personalised shortcut keys to functions they frequently use to enhance keyboard navigation. Others memorise the steps to reach certain pages or to complete processes on a website. Both rely on predictable and consistent functionality.

Help users avoid and correct mistakes

Forms and other interaction can be confusing or difficult to use for many people, and, as a result, they may be more likely to make mistakes. Examples of helping users to avoid and correct mistakes include:

  • Descriptive instructions, error messages, and suggestions for correction
  • Context-sensitive help for more complex functionality and interaction
  • Opportunity to review, correct, or reverse submissions if necessary

Meeting this requirement helps people who do not see or hear the content, and may not recognise implicit relationships, sequences, and other cues. It also helps people who do not understand the functionality, are disoriented or confused, forget, or make mistakes using forms and interaction for any other reason.

Content reproduced from World Wide Web Consortium (W3C) website