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What is WCAG?

WCAG stands for Web Content Accessibility Guidelines. It's a set of recommendations published by the W3C, the organization that oversees web standards, to help make web content accessible to people with disabilities.

The current version is WCAG 2.2, published in October 2023. It contains 86 individual success criteria, organized around four core principles.

The Four Principles (POUR)

Every success criterion in WCAG belongs to one of four principles, remembered by the acronym POUR. Think of these less as rules and more as a way of asking: can this person actually use what I've built?

Perceivable
Information and interface components must be presentable in ways users can perceive. If someone can't see your image, they need a text description. If someone can't hear your audio, they need captions or a transcript. The content has to reach them somehow.
Operable
Users must be able to operate the interface. This means everything that works with a mouse must also work with a keyboard alone. It means giving people enough time to read and respond. It means not designing things that cause seizures.
Understandable
Content and controls must be understandable. Pages should declare their language. Navigation should be consistent. Errors should explain what went wrong and how to fix it, not just turn a field red.
Robust
Content must work reliably across different browsers and assistive technologies. Every interactive element needs an accessible name, a role, and a state: the building blocks that screen readers depend on.

Conformance Levels: A, AA, AAA

WCAG criteria are grouped into three levels. Each level builds on the one below it.

WCAG 2.2 conformance levels
Level What it means Criteria count
A The minimum. Failing these criteria creates serious barriers for at least some group of users. All 30 must pass for any conformance claim. 30
AA The practical standard. Required by Section 508, the EU's EAA, and most legal accessibility frameworks worldwide. Includes all 30 Level A criteria plus 24 more. 54 total
AAA Enhanced accessibility, going beyond the legal minimum. Worthwhile to pursue where possible, but W3C does not recommend requiring AAA conformance as a blanket site-wide policy. 86 total

Important: Conformance is all-or-nothing per level. Satisfying 53 of 54 Level A+AA criteria is not AA conformance. All criteria at the claimed level must pass, across the entire page.

Why WCAG Matters in Practice

Accessibility isn't just about legal compliance, though that matters too. It's about whether real people can use what you've made.

Consider: a keyboard-only user who can't reach your navigation, a screen reader user who hears "button button button" because nothing has a name, or someone with low vision whose text disappears when they zoom in. WCAG is a framework for catching these problems before they ship.

Beyond disability: captions help in noisy environments. Good color contrast helps in sunlight. Keyboard navigation helps power users. Most accessibility improvements help everyone.

What's New in WCAG 2.2

WCAG 2.2, published October 2023, added nine new success criteria compared to WCAG 2.1, and retired one (SC 4.1.1 Parsing, which was made obsolete by modern browser error correction).

The six new Level A and AA criteria most likely to affect day-to-day work: