WCAG Layers of Guidance

Four Principles of WCAG

The Web Content Accessibility Guidelines (WCAG) consist of four principles that form the acronym POUR.
For a quick overview of the WCAG principles, see WCAG at a Glance.


How does your audience perceive the digital content you create and share?
Should they be able to see it? Hear it? Both?
What if they have vision and/or hearing loss?
Are there alternative modes of representation?

There are four guidelines and 20 A and AA success criteria for Perceivable.


How does your audience operate within your digital content?
Does it depend entirely on using a mouse?
What if they don’t use a mouse?
Can they use a keyboard instead?
What about a touch screen, or voice commands?

There are five guidelines and 17 A and AA success criteria for Operable.


Is your content understandable to your whole audience?
Is it readable? What if their first language is not the primary language of the instructions?
Are there guides for understanding acronyms, abbreviations, and jargon?
Is everything arranged consistently and predictably?

There are three guidelines and 10 A and AA success criteria for Understandable.


Is the platform and content created in a way that works for everyone, including people who use assistive and mobile technologies?

There is one guideline and 3 A and AA success criteria for Robust.

Success Criteria

Each of the four WCAG principles has its own set of guidelines and Success Criteria (SC).
Each SC also includes a list of technology-specific techniques for meeting it.

In total, there are 78 Success Criteria in the WCAG 2.1 standard.
SC categorized by three levels of conformance: A, AA and AAA.
Note that Rice Policy 851 does not require us to meet AAA success criteria.

There are 50 A and AA criteria.
Some A and AA SC are more relevant to admins, developers, and technology vendors who provide products and tools.
Content authors can meet many of the SC relevant to your role by using the basic techniques.

3 Levels of Conformance

LEVEL A, success criteria you MUST meet.
Level A criteria form the baseline for digital accessibility.
The techniques associated with level A show us how to avoid designing barriers into our digital information and help us comply with nondiscrimination laws.

LEVEL AA, success criteria you SHOULD meet.
Level AA criteria go beyond baseline requirements.
AA criteria help improve the quality of our digital information without requiring significantly more effort.
Rice University asks us to meet level AA criteria whenever relevant to the digital information we create and share.

LEVEL AAA, success criteria you COULD meet.
Level AAA criteria go even further and empower our audience with greater choices.
Rice University does not require us to meet Level AAA criteria, but encouraged whenever possible.


There are dozens of individual techniques in WCAG 2.1.
Each technique is a technology-specific recommendation for meeting a success criterion (SC).
Each SC can have multiple techniques depending on the context and technology.
It is important to note that techniques themselves are not required. Meeting SC is required.

Learn more about WCAG techniques.

Basics Technique Guides

The following guides are designed to help content authors meet WCAG 2.1 A-AA success criteria.

Guides on Forms and Mobile Checks coming soon.