Understanding the POUR Principles of Accessibility
The 4 Principles of Accessibility
Perceivable – Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to understand the information being presented; it can’t be invisible to any of their senses.
Perceivable Guideline Example: 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, translations, or simpler language.
Operable – User interface components and navigation must be operable. This means that users must be able to use the interface and it cannot require interaction that a user cannot perform.
Operable Guideline Example: Keyboard Accessible. Make all functionality available from a keyboard or a keyboard interface so that people with disabilities are able to operate websites without needing a mouse.
Understandable – Information and the operation of user interfaces must be understandable. This means that users must be able to comprehend information as well as how to use the interface.
Understandable Guideline Example: Labels and Instructions. Labels and instructions are provided to users whenever content requires user input, e.g. sign up or login forms.
Robust – Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies. This means as technologies and user agents advance and evolve, content should remain accessible.
Robust Guideline Example: Parsing. Maximise compatibility with current and future user agents, including assistive technologies, by ensuring content created using markup languages are coded correctly and have complete start and end tags. This allows user agents to present content without crashing.
POUR and the 3 levels of Compliance
These guidelines work with a ‘success criteria’ organised into three levels of compliance: A, AA, AAA. Level A and Level AA have been adopted by various international standards and legal requirements.
For more details on the differences between the three levels of WCAG compliance, read our blog post on what is the difference between WCAG A, AA, and AAA guidelines.