WCAG Guidelines Explained: Principles, Levels and Who Must Comply

Last updated: October 13, 2026

Short answer: the WCAG guidelines (Web Content Accessibility Guidelines) are the W3C standard for accessible websites, apps and documents. The current version is WCAG 2.2, published on 5 October 2023. It is built on 4 principles (perceivable, operable, understandable, robust), 13 guidelines, and testable success criteria at three levels: A, AA and AAA. Most laws require Level AA.

This guide explains each part, what changed in WCAG 2.2, which laws require which version, and the AA failures we find most often when we scan real websites.

What Are the WCAG Guidelines?

WCAG is published by the World Wide Web Consortium (W3C) through its Web Accessibility Initiative (WAI). It defines how to make web content usable by people with visual, auditory, motor and cognitive disabilities, including people who use screen readers, keyboard-only navigation, voice control or screen magnification.

WCAG is organised in four layers:

1. Principles: the 4 POUR principles.
2. Guidelines: 13 goals grouped under the principles.
3. Success criteria: testable pass/fail statements, such as 1.4.3 Contrast (Minimum). Each one has a level: A, AA or AAA.
4. Techniques: informative examples of how to meet each criterion.

Only the success criteria are tested. When a law or contract says "WCAG 2.1 AA", it means every Level A and Level AA success criterion in WCAG 2.1. For a plain-language definition, see what WCAG means.

WCAG Versions: 2.0, 2.1, 2.2 and 3.0

Version	Published	What it added
WCAG 2.0	December 2008	The 4 principles, 12 guidelines and the A/AA/AAA levels. Still the version cited by Section 508 and AODA.
WCAG 2.1	June 2018	Guideline 2.5 Input Modalities, plus criteria for mobile, low vision and cognitive needs (reflow, text spacing, non-text contrast, orientation). Cited by the ADA Title II rule and EN 301 549.
WCAG 2.2	5 October 2023	9 new success criteria (focus, target size, dragging, help, authentication) and removed 4.1.1 Parsing as obsolete.
WCAG 3.0	Working draft	A new model with different scoring. It is not a finished standard and no law requires it.

Each 2.x version is backward compatible: a page that meets WCAG 2.2 AA also meets WCAG 2.1 AA and 2.0 AA (with the one exception of 4.1.1 Parsing, which 2.2 dropped). That is why building to WCAG 2.2 AA is the simplest target: it covers every law below.

The Four Principles (POUR) and the 13 Guidelines

Every WCAG guideline sits under one of four principles. If content fails one principle, some users cannot use it at all.

1. Perceivable

Users must be able to perceive the information with the senses they have.

• 1.1 Text Alternatives: alt text for images and other non-text content.
• 1.2 Time-based Media: captions, transcripts and audio description for audio and video.
• 1.3 Adaptable: structure (headings, lists, tables, labels) that assistive technology can read.
• 1.4 Distinguishable: colour contrast, resizable text, reflow and no information by colour alone.

2. Operable

Users must be able to operate every control and navigate the page.

• 2.1 Keyboard Accessible: every function works with a keyboard, with no keyboard traps.
• 2.2 Enough Time: users can extend or turn off time limits and pause moving content.
• 2.3 Seizures and Physical Reactions: nothing flashes more than three times per second.
• 2.4 Navigable: skip links, page titles, logical focus order, clear link text and visible focus.
• 2.5 Input Modalities: pointer gestures, target size and dragging alternatives.

3. Understandable

Users must be able to understand the content and how the interface behaves.

• 3.1 Readable: the page language is set, and unusual words are explained.
• 3.2 Predictable: consistent navigation, and no unexpected changes on focus or input.
• 3.3 Input Assistance: labels, instructions, clear error messages and error prevention.

4. Robust

Content must work with current and future browsers and assistive technologies.

• 4.1 Compatible: every control exposes its name, role and value, and status messages are announced.

WCAG Conformance Levels: A, AA and AAA

• Level A: the minimum. Failing a Level A criterion usually blocks some users completely, for example a button that cannot be reached by keyboard.
• Level AA: the level that laws, procurement rules and most contracts require. It includes everything in Level A plus criteria such as 4.5:1 text contrast and visible focus.
• Level AAA: the highest level. W3C does not recommend AAA as a general policy for whole sites, because some content cannot meet it. No major law requires it.

For a criterion-by-criterion list at Level AA, see our WCAG 2.1 AA guide.

What Is New in WCAG 2.2

WCAG 2.2 added 9 success criteria. Six of them are Level A or AA, so they matter for compliance:

• 2.4.11 Focus Not Obscured (Minimum) (AA): sticky headers and cookie banners must not completely hide the focused element.
• 2.5.7 Dragging Movements (AA): anything done by dragging also works with a single click or tap.
• 2.5.8 Target Size (Minimum) (AA): click targets are at least 24 by 24 CSS pixels, or have enough space around them.
• 3.2.6 Consistent Help (A): help links and contact options appear in the same place on each page.
• 3.3.7 Redundant Entry (A): users are not asked to type the same information twice in one process.
• 3.3.8 Accessible Authentication (Minimum) (AA): logins do not depend on memory tests or puzzles without an alternative, and password managers and paste must work.

The other three (2.4.12, 2.4.13 and 3.3.9) are Level AAA. WCAG 2.2 also removed 4.1.1 Parsing. Our WCAG 2.2 practical guide shows how to test each new criterion.

Is WCAG Mandatory? Who Must Follow the WCAG Guidelines

WCAG itself is a standard, not a law. It becomes mandatory when a law, regulation or contract adopts it. Each law names its own version:

Law	Who it covers	WCAG version
ADA Title II (US)	State and local governments, including public schools, colleges and transit	WCAG 2.1 AA. Compliance dates: April 26, 2027 for entities with 50,000 or more people, and April 26, 2028 for smaller entities and special districts.
ADA Title III (US)	Businesses open to the public	No technical standard in the regulation. Demand letters, settlements and DOJ guidance use WCAG AA as the benchmark.
Section 508 (US)	Federal agencies and the technology they buy	WCAG 2.0 AA
European Accessibility Act (EU)	Products and services such as e-commerce, banking and e-books, since June 28, 2025	WCAG 2.1 AA through EN 301 549
AODA (Ontario, Canada)	Public sector and organisations with 50 or more employees	WCAG 2.0 AA

The ADA Title II dates come from the Department of Justice interim final rule published on April 20, 2026, which extended the original deadlines (ada.gov). Federal Section 508 rules are at section508.gov.

If you sell software to government or enterprise buyers, they will usually ask for a VPAT or Accessibility Conformance Report that maps your product against these criteria. See how we prepare a VPAT/ACR.

The WCAG Failures We Find Most Often

We scanned 1,777 websites with the WebAbility scanner between June 2025 and August 2026. These were the most common Level A and AA failures, with the share of sites affected:

#	Failure	WCAG	Sites affected
1	Text contrast below 4.5:1	1.4.3	57%
2	No visible keyboard focus indicator	2.4.7	53%
3	Structure not conveyed in markup	1.3.1	51%
4	Custom controls missing name, role or value	4.1.2	37%
5	Images missing alt text	1.1.1	30%
6	Functionality not reachable by keyboard	2.1.1	28%
7	Empty or ambiguous link text	2.4.4	24%
8	UI component contrast below 3:1	1.4.11	24%
9	Reading order does not match visual order	1.3.2	18%
10	Unhelpful headings or labels	2.4.6	12%

Full method and more data: State of Web Accessibility 2026. To check contrast pairs one by one, use the free WCAG contrast checker.

How to Meet the WCAG Guidelines

1. Pick your target. Use WCAG 2.2 AA unless a contract names a different version.
2. Run an automated scan. Automated tools reliably catch about 30 to 40% of issues, such as contrast, missing alt attributes and unlabelled fields. Start with our free website accessibility checker.
3. Test by hand. Navigate every key flow with only a keyboard, then with a screen reader such as NVDA or VoiceOver. This finds the issues no scanner can judge, such as whether alt text is meaningful.
4. Fix in the source. Fix templates and shared components first, so one change fixes every page that uses them.
5. Document it. Publish an accessibility statement and, for B2B software, a VPAT/ACR.
6. Monitor. New pages, plugins and content reintroduce issues. Rescan on a schedule.

If you need a report you can hand to a buyer, auditor or lawyer, our manual WCAG audit covers all Level A and AA criteria with assistive-technology testing.

Tools That Help You Follow WCAG

• WebAbility free checker: runs axe-core, HTML_CodeSniffer and our own checks in one scan, with no account.
• WAVE: a browser extension that marks issues on the page.
• axe DevTools: developer testing in browser DevTools.
• Lighthouse: Chrome's built-in accessibility audit.
• NVDA, JAWS and VoiceOver: screen readers for manual testing.

For a full comparison, see web accessibility testing tools.

Common Mistakes When Applying WCAG

• Treating a clean automated scan as proof of compliance.
• Adding ARIA where native HTML elements would work, which often makes things worse.
• Removing focus outlines for design reasons without a visible replacement.
• Testing desktop only, and missing reflow and target size on mobile.
• Fixing once and never retesting after new content or features ship.

Why WCAG Matters Beyond the Law

About 1.3 billion people, or 1 in 6 people worldwide, live with a significant disability (WHO). The same changes that help them, such as clear headings, descriptive links, readable contrast and forms that explain errors, make sites easier for everyone and easier for search engines to understand.

Frequently Asked Questions

Who is required to follow WCAG?

In the US, state and local governments under ADA Title II (WCAG 2.1 AA) and federal agencies under Section 508 (WCAG 2.0 AA). Businesses open to the public are expected to be accessible under ADA Title III, and WCAG AA is the benchmark used in practice. In the EU, businesses covered by the European Accessibility Act must meet EN 301 549, which uses WCAG 2.1 AA.

What is POUR in WCAG?

POUR stands for the four WCAG principles: Perceivable, Operable, Understandable and Robust. Every guideline and success criterion sits under one of them.

Is WCAG mandatory in the USA?

Yes for some organisations. The ADA Title II rule requires WCAG 2.1 AA for state and local governments, and Section 508 requires WCAG 2.0 AA for federal agencies. For private businesses, the ADA requires accessibility but does not name a version, so courts and settlements use WCAG AA.

Is WCAG 3.0 released?

No. WCAG 3.0 is a W3C working draft. WCAG 2.2 is the current W3C Recommendation, and no law requires WCAG 3.0.

What WCAG level do I need?

Level AA. It is the level every major accessibility law uses. Level AAA is not required by law and is not recommended as a whole-site target.

How many WCAG guidelines are there?

WCAG 2.1 and 2.2 have 13 guidelines under 4 principles. WCAG 2.0 has 12; 2.1 added guideline 2.5 Input Modalities.