WCAG Overview

The Web Content Accessibility Guidelines (WCAG) are the international technical standard for web accessibility. They define what it means for web content to be accessible and provide testable criteria for measuring conformance. When Canadian law requires “accessible web content,” WCAG is the standard it references.

Who creates WCAG?

WCAG is produced by the W3C Web Accessibility Initiative (WAI), a program of the World Wide Web Consortium. The W3C is the international standards body responsible for most web standards, including HTML and CSS.

WAI brings together:

  • Disability advocacy organizations
  • Assistive technology vendors (screen reader developers, etc.)
  • Web browser makers
  • Government representatives
  • Independent researchers and practitioners
  • Industry representatives from companies that build the web

The development process is open and consensus-driven. New versions go through multiple public review rounds before publication.

The POUR principles

WCAG organizes all accessibility requirements around four high-level principles known as POUR:

PrincipleMeaning
PerceivableUsers must be able to perceive the information presented — it cannot be invisible to all their senses
OperableUsers must be able to operate the interface — it cannot require interaction they cannot perform
UnderstandableUsers must be able to understand the information and the operation of the interface
RobustContent must be robust enough to be interpreted by a wide variety of assistive technologies

Every WCAG success criterion is organized under one of these four principles.

Structure: Principles → Guidelines → Success Criteria

WCAG has a three-level structure:

Principles (4)

The four POUR principles described above.

Guidelines (13 in WCAG 2.1)

Each principle contains guidelines — broad statements about what to achieve. For example, Guideline 1.1 states: “Provide text alternatives for any non-text content.” Guidelines are not testable themselves; they provide the organizing framework.

Success Criteria (78 in WCAG 2.1)

Success criteria are the testable statements — the specific requirements your content must meet. Each criterion is assigned a level: A, AA, or AAA.

Example:

  • Principle: Perceivable
  • Guideline: 1.1 Text Alternatives
  • Success Criterion: 1.1.1 Non-text Content (Level A) — “All non-text content that is presented to the user has a text alternative that serves the equivalent purpose.”

Conformance levels

WCAG defines three levels of conformance:

LevelDescription
AThe minimum level. Addresses the most critical barriers — content that is impossible to use without remediation.
AAThe widely adopted standard. Addresses significant barriers while remaining achievable for most organizations. Required by Canadian law.
AAAThe highest level. Addresses additional barriers for specific disability groups. Not all content can meet AAA, and it is not typically required by law.

Conformance is cumulative: Level AA requires meeting all Level A and all Level AA criteria. Level AAA requires meeting all three levels.

See WCAG Levels Explained for detailed examples of each level.

WCAG versions

Developer Leadership
VersionPublishedKey additions
WCAG 1.01999Original — HTML-focused, technology-specific
WCAG 2.02008Technology-neutral, testable criteria, POUR structure
WCAG 2.1201817 new criteria for mobile, cognitive, and low vision
WCAG 2.220239 new criteria focused on cognitive and motor disabilities; removes 4.1.1 Parsing
WCAG 3.0In developmentMajor rethink of structure and testing model; not yet stable

How WCAG connects to Canadian law

WCAG is not itself Canadian law — it is a technical standard. Canadian laws reference WCAG in different ways:

LawWCAG reference
Accessible Canada Act (ACA)References EN 301 549, which incorporates WCAG 2.1 Level AA
AODA (Ontario)Explicitly requires WCAG 2.0 Level AA
Government of Canada Standard on Web AccessibilityRequires WCAG 2.0 Level AA (update to 2.1 in progress)
Canadian Human Rights ActNo specific WCAG level — reasonableness test, but WCAG is used as the benchmark
Accessible BC ActStandards in development, expected to reference WCAG 2.1 AA
Accessibility for Manitobans ActReferences WCAG 2.0 Level AA

Supporting documents

WCAG is accompanied by several key supporting documents:

Understanding WCAG

For each success criterion, the W3C publishes an Understanding document explaining the intent, who benefits, and what counts as a failure. These are essential for implementors and auditors.

Techniques for WCAG

Techniques documents provide specific, technology-specific methods for satisfying success criteria — including sufficient techniques (that pass) and advisory techniques (that improve accessibility beyond the criteria). Techniques are informative, not normative.

How to Meet WCAG (Quick Reference)

A customizable, filterable reference that lets you filter criteria by level, technology, and disability type. Available at w3.org/WAI/WCAG21/quickref/.

Accessibility Conformance Reports (ACR / VPAT)

Organizations often need to report their WCAG conformance level using a Voluntary Product Accessibility Template (VPAT) or Accessibility Conformance Report (ACR). These are structured documents listing each success criterion and the organization’s conformance status.

Common misconceptions

Does WCAG compliance mean my site is fully accessible?

WCAG compliance is a strong indicator of accessibility, but it is not a guarantee. Automated tools can detect about 30–40% of WCAG failures. Manual testing, including testing with real assistive technology users, is needed to catch the rest. A site can technically pass all testable criteria and still have usability barriers for people with disabilities.

Is WCAG only for blind users?

WCAG addresses barriers for users with visual, auditory, motor, cognitive, neurological, and speech disabilities. Many criteria — such as keyboard operability, plain language, and predictable navigation — primarily benefit users with motor or cognitive disabilities, not visual disabilities.

Once we pass WCAG, are we done?

No. Accessibility is an ongoing practice. Every new feature, content update, or third-party integration is an opportunity to introduce new barriers. Regular auditing, developer training, and including accessibility in design review processes is needed to maintain conformance over time.

Is WCAG 3.0 coming soon? Should we wait?

WCAG 3.0 is under active development but is not expected to be stable and legally referenced for several years. It represents a significant structural change (moving from pass/fail to a scoring model) and will likely have a long transition period. Continue targeting WCAG 2.1 Level AA — it will not become obsolete when WCAG 3.0 publishes.