WCAG principles
There are four basic principles in WCAG 2.1, designed to help you think about the ways people interact with content:
- Perceivable
- Operable
- Understandable
- Robust
For example, people might:
- Listen to content, look at it, or feel it with their fingertips.
- Use a keyboard, voice commands, or a mouse or touch only with difficulty.
- Understand content only when it’s simple, consistent, and familiar.
- Access content with browsers and assistive technologies that are old or out of date.
The principles apply to every part of your service, including code, content, and interactions. This means everyone on your team needs to understand and consider them.
WCAG Guidelines
WCAG 2.1 has 12 guidelines that support the four principles. Each guideline is broken down into specific requirements (known as Success Criteria or SC) that your service must meet.
The WebAIM WCAG checklist uses plain language to make the WCAG principles, guidelines, and SC, easier to understand.
WCAG Levels
Each SC is assigned a conformance level: A, AA, or AAA. There are:
- 30 SC at Level A (the most basic level).
- 20 SC at*Level AA (the level required by policies and laws).
- 28 SC at Level AAA (only applicable under certain circumstances).
To meet WCAG 2.1 Level AA, your service must meet all applicable Level A SC and all applicable Level AA SC.
Note: Not all SC are applicable all of the time. If your service contains no multimedia content, the SC relating to multimedia will not be applicable for example.