Everything
The following is every single WCAG criterion in version 2.2. Contrary to popular belief, level AAA is not always hard or impossible to meet. There are many technical reasons why items will be designated as AAA, but what I have experienced over time is a lot of these are just included as part of good design and usability.
Not all guidelines are applicable to every site. That doesn't mean you can't meet AAA. Some guidelines are AAA because they require extra effort and resources that may be difficult or excessive for most sites. If your content is vital, or maybe something someone paid for, then you should consider extending the effort. The purpose of all the guidelines are to increase usability for everyone. So if that is important to you and you have the resources, go for. Keep the people consuming your content in mind and use your best human-focused judgement. You could level up from removing barriers to potentially reducing friction.
To be clear, accessibility is not a checklist or a tool, and doing everything exacly as documented here will not always guarantee an accessible, or compliant site. It's important to note that how you deliver accessibility is unique and completely dependant on your particular site content, and users.
Ensure everyone can perceive content
Based on the Perceivable principle:
Information and user interface components must be presentable to users in ways they can perceive.
Color
Semantics
Static content
Images
Audio and video
- 1.2.1 Audio/Video-only Prerecorded (A)
- 1.2.9 Audio-only - Live (AAA)
- 1.2.2 Captions - Prerecorded (A)
- 1.2.4 Captions - Live (AA)
- 1.2.3 Audio Description or Media Alternative - Prerecorded (A)
- 1.2.5 Audio Description - Prerecorded (A)
- 1.2.7 Extended Audio Description - Prerecorded (AAA)
- 1.2.8 Media Alternative - Prerecorded (AAA)
- 1.4.2 Audio Control (A)
- 1.4.7 Low or No Background Audio (AAA)
- 1.2.6 Sign Language - Prerecorded (AAA)
Responsive web design and accessibility
Ensure everyone can interact with content
Based on the Operable principle:
User interface components and navigation must be operable.
Ways of navigating
Ways of interacting: Keyboard and focus
Ways of interacting: Touch and mouse
Animations
Time limits
Ensure everyone can understand content
Based on the Understandable principle:
Information and the operation of the user interface must be understandable.
Content
Consistency
Context switching
Forms
- 3.3.2 Labels or Instructions (A)
- 3.3.1 Error Identification (A)
- 3.3.3 Error Suggestion (AA)
- 3.3.4 Error Prevention - Legal, Financial, Data (AA)
- 3.3.6 Error Prevention - All (AAA)
- 3.3.5 Help (AAA)
- 3.3.7 Redundant Entry (A)
- 3.3.8 Accessible Authentication - Minimum (AA)
- 3.3.9 Accessible Authentication - Enhanced (AAA)
Ensure content is robust
Based on the Robust principle:
Content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies.