The four principles of accessibility
Web Content Accessibility Guidelines (WCAG) is an international system of coding standards. This set of requirements ensures that a website is accessible by everyone. WCAG has defined The Four Principles of Accessibility: Perceivable, Operable, Understandable and Robust.
People need to be able to perceive web content. If the only way a website can be perceived is with sight, then those who are blind cannot perceive it. If the only way content can be perceived is with hearing, then a deaf person will not be able to access that information. Everyone does not have the same abilities. Accessibility ensures that information can be perceived in multiple ways.
A standard keyboard and mouse are not the only way that people access the web. Yet we continue to build websites that are mouse-dependent. Alternative devices accommodate a variety of disabilities, and most of them emulate keyboard functionality. Therefore, wherever possible, content should be operable through a keyboard or keyboard interface.
Alternative representations of information can increase understandability, as do concise summaries of lengthy content. In addition, navigation and interactive elements should be consistent and predictable.
When web content requires a specific technology, some users will be excluded. When they are allowed to choose their own technologies, they can customize it to meet their needs. Overall, the more control the user has, the more likely they will be able to access the content in the way that suits them best.
By following these four principles, we move closer to creating an environment that can be accessed, understood and used by all people, regardless of ability or disability. Learn more about the current WCAG 2.1 guidelines by visiting the WC3 website.