Understanding the Four Principles of Accessibility
The guidelines and success criteria are organized around the following four principles, which lay the foundation necessary for anyone to access and use digital content.
Content must be:
Perceivable
Information must be presented to users in ways they can perceive; it cannot be invisible to all of their senses.
- Provide text alternatives for non-text content.
- Provide captions and other alternatives for multimedia.
- Create content that can be presented in different ways, including by assistive technologies, without losing meaning.
- Make it easier for users to see and hear content.
Operable
User interface components and navigation must be operable; the interface cannot require interaction that a user cannot perform.
- Make all functionality available from a keyboard.
- Give users enough time to read and use content.
- Do not use content that causes seizures.
- Help users navigate and find content.
Understandable
Information and the operation of user interface must be understandable.
- Make text readable and understandable.
- Make content appear and operate in predictable ways.
- Help users avoid and correct mistakes.
Robust
Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies. Users must be able to access the content as technologies advance.
- Maximize compatibility with current and future user tools.