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WCAG explained: principles, levels and versions

Quick answer

WCAG is the Web Content Accessibility Guidelines, the international standard from W3C for making web content more accessible to people with disabilities. Every requirement in it has a level: A, AA or AAA. WCAG 2.2 is the latest version, and Level AA is the level named by every rule on this page that names a WCAG version.

Facts last checked

The four principles

Every WCAG requirement sits under one of four principles.

  • Principle 1

    Perceivable

    People can see or hear the content, or get it another way. A photo on a menu page has a text description.

  • Principle 2

    Operable

    People can use every control and get around. A booking form works with a keyboard, not just a mouse.

  • Principle 3

    Understandable

    People can follow what the page says and does. A checkout says which field has a mistake and how to fix it.

  • Principle 4

    Robust

    The code works with the browsers and assistive technology people use, such as a screen reader.

Success criteria under each principle in WCAG 2.2
  • Perceivable: 29
  • Operable: 34
  • Understandable: 21
  • Robust: 2

Source: W3C, WCAG 2.2. Counted from the published standard.

How a criterion is numbered

Each requirement is called a success criterion. Its number tells you where it sits in WCAG.

How to read 1.4.3
Principle
1
Guideline
.4
Criterion
.3

  • 4

    principles, the top layer. The first digit picks one: 1 is Perceivable.

    W3C, WCAG 2.2

  • 13

    guidelines, the goals under each principle. 1.4 is Distinguishable.

    W3C, WCAG 2.2

  • 86

    success criteria, the requirements a page is tested against. 1.4.3 is Contrast (Minimum).

    W3C, WCAG 2.2

The full line, as a report writes it
Number
1.4.3
Name
Contrast (Minimum)
Level
Level AA

Three levels

Level A is the lowest and AAA is the highest. Each level includes the ones below it.

Success criteria at each level of WCAG 2.2
  • Level A: 31
  • Level AA: 24
  • Level AAA: 31

Source: W3C, WCAG 2.2. Counted from the published standard.

What Level AA meansA page meets Level AA when it meets every Level A and every Level AA criterion: 55 in WCAG 2.2. Each rule in the last section of this guide that names a WCAG version asks for Level AA.

About Level AAAW3C does not recommend requiring Level AAA across a whole site, because some content can't meet every AAA criterion.

Versions

Each WCAG 2 version builds on the one before it.

  1. May 1999Standard

    WCAG 1.0

  2. December 2008Standard

    WCAG 2.0

  3. June 2018Standard

    WCAG 2.1

    Added 17 success criteria and a new guideline on input beyond the keyboard.

  4. October 2023Standard

    WCAG 2.2

    The latest version. It added 9 success criteria and removed one.

  5. October 2025Standard

    WCAG 2.2 becomes an ISO standard

    WCAG 2.2 is approved as the international standard ISO/IEC 40500:2025.

  6. September 2026Draft

    WCAG 3.0, latest working draft

    W3C calls it "an incomplete draft that will change".

Success criteria in each version of WCAG 2
  • WCAG 2.0: 61
  • WCAG 2.1: 78
  • WCAG 2.2: 86

Source: W3C, WCAG 2.0, 2.1 and 2.2. Counted from each published standard.

What about WCAG 3W3C says WCAG 3 "is not expected to be a completed W3C standard for a few more years", and that WCAG 2 will not be retired for several years after WCAG 3 is finished.

What WCAG 2.2 added

Most are about keyboard focus, pointer targets and logging in.

Success criteria new in WCAG 2.2
Success criterionLevelIn plain words
2.4.11 Focus Not Obscured (Minimum)AAThe item with keyboard focus is at least partly visible.
2.4.12 Focus Not Obscured (Enhanced)AAAThe item with keyboard focus is fully visible.
2.4.13 Focus AppearanceAAAThe focus indicator is large enough and has enough contrast.
2.5.7 Dragging MovementsAAAnything done by dragging can also be done a simpler way, such as a tap.
2.5.8 Target Size (Minimum)AAButtons and links are big enough, or have enough space around them.
3.2.6 Consistent HelpAHelp sits in the same place on every page that has it.
3.3.7 Redundant EntryAPeople aren't asked for the same information twice in one session.
3.3.8 Accessible Authentication (Minimum)AALogging in doesn't make people solve, remember or retype something.
3.3.9 Accessible Authentication (Enhanced)AAALogging in doesn't make people recognize objects or their own images.

Source: W3C WAI, What's New in WCAG 2.2

One criterion removedWCAG 2.2 also removed 4.1.1 Parsing. W3C says the problems it covered no longer exist or are covered by other criteria.

Which rules name which version

WCAG 2.0, 2.1 and 2.2 are all existing standards. Rules written at different times name different ones.

The WCAG version and level each rule names
RuleWho it coversWCAG version and level
ADA Title IIIBusinesses open to the publicNone in the regulation. Department of Justice guidance calls WCAG "helpful guidance".
ADA Title II web ruleState and local governmentsWCAG 2.1, Level A and AA
HHS Section 504 ruleOrganizations that receive HHS fundingWCAG 2.1, Level A and AA
Section 508 standardsU.S. federal agenciesWCAG 2.0, Level A and AA
Air Carrier Access Act website ruleAirlines that fly at least one plane with more than 60 seatsWCAG 2.0, Level AA
New York State policy NYS-P08-005New York State government websitesWCAG 2.2, Level AA
EN 301 549 V3.2.1 (2021)European standard. Still the EU's reference version as of September 2026.WCAG 2.1, Level AA
EN 301 549 V4.1.1 (2026)European standard, newest versionWCAG 2.2, Level AA

Source: eCFR, ADA.gov, U.S. Access Board, New York State ITS, ETSI and AccessibleEU

What we test againstWe test against WCAG 2.2 Level AA. W3C says content that meets WCAG 2.2 also meets 2.1 and 2.0, so the same test covers the WCAG criteria in each version named above. Which rule applies to you is a legal question, and your attorney decides those.

Sources

  1. W3C WAI, WCAG 2 Overview (2026)
  2. W3C, Web Content Accessibility Guidelines (WCAG) 2.2 (2024)
  3. W3C, Web Content Accessibility Guidelines (WCAG) 2.1 (2025)
  4. W3C, Web Content Accessibility Guidelines (WCAG) 2.0 (2008)
  5. W3C, Web Content Accessibility Guidelines 1.0 (1999)
  6. W3C WAI, What's New in WCAG 2.2 (2023)
  7. W3C, press release on WCAG 2.2 as ISO/IEC 40500:2025 (2025)
  8. W3C WAI, WCAG 3 Introduction (2026)
  9. W3C, W3C Accessibility Guidelines (WCAG) 3.0, Working Draft (2026)
  10. U.S. Department of Justice, Guidance on Web Accessibility and the ADA (2022)
  11. eCFR, 28 CFR 35.200: ADA Title II web and mobile app rule (2026)
  12. eCFR, 45 CFR 84.84: HHS Section 504 web and mobile app rule (2026)
  13. U.S. Access Board, ICT Standards and Guidelines (Revised 508 Standards) (2017)
  14. eCFR, 14 CFR 382.43: Air Carrier Access Act website rule (2026)
  15. New York State Office of Information Technology Services, policy NYS-P08-005 (2024)
  16. ETSI, CEN and CENELEC, EN 301 549 V3.2.1 (2021)
  17. ETSI, CEN and CENELEC, EN 301 549 V4.1.1 (2026)
  18. AccessibleEU (European Commission), notice on the EN 301 549 update (2026)

We provide technical accessibility services, not legal advice.

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