Learn · WCAG
What Is WCAG?
WCAG stands for Web Content Accessibility Guidelines - the international standard that defines what makes a website accessible to people with disabilities. Published by the W3C, WCAG is the benchmark behind ADA compliance, AODA requirements, and Section 508 obligations worldwide.
The Basics
WCAG in plain language.
The Web Content Accessibility Guidelines are a set of technical criteria that describe how websites, web apps, and digital content should be built so that people with disabilities can use them. They're developed by the World Wide Web Consortium (W3C) through its Web Accessibility Initiative (WAI) - the same organization that defines HTML, CSS, and the core standards of the web.
The W3C Web Accessibility Initiative
The W3C is the international body that maintains the web's core standards. WCAG is developed through a collaborative process involving disability advocates, browser vendors, developers, and government agencies - which is why it's referenced in laws across more than 40 countries.
No - but laws require it
WCAG itself is a technical standard, not legislation. But the Americans with Disabilities Act (ADA), Canada's AODA, the EU's EN 301 549, and the US Section 508 all cite WCAG as the benchmark for what "accessible" means in practice. Meeting WCAG is how you demonstrate legal compliance.
The Four Principles
WCAG is built on four principles - POUR.
Every WCAG success criterion maps back to one of four core principles. If your site violates any of them, it may be inaccessible - and non-compliant.
Perceivable
Information and UI components must be presentable in ways users can perceive. If someone can't see your image, does it have alt text? If someone can't hear your video, does it have captions?
Operable
Users must be able to operate all UI components and navigate the site. Everything clickable must be reachable by keyboard. Nothing should require a mouse, precise pointing, or timing.
Understandable
Content and UI operation must be understandable. Text must be readable, pages must behave predictably, and forms must help users avoid and correct mistakes.
Robust
Content must be robust enough to be reliably interpreted by a wide variety of assistive technologies - today and as those tools evolve. This is where ARIA roles, semantic HTML, and valid markup matter.
Conformance Levels
Level A, AA, and AAA - what's the difference?
Each WCAG success criterion is assigned a conformance level. Most legal requirements and court decisions reference Level AA as the expected standard for public-facing websites.
The minimum baseline
Level A criteria address the most critical barriers - failures that make a page completely unusable for some users. Examples: images without alt text, video with no audio alternative, content that flashes at seizure-triggering rates. Failing Level A means significant portions of your site are effectively inaccessible.
The legal standard
Level AA builds on Level A and addresses the most common accessibility barriers in practice. This is the level required by ADA litigation precedent, AODA, Section 508, and most international accessibility laws. It includes colour contrast ratios, keyboard accessibility, form labels, focus visibility, and more. WCAG 2.2 AA is the current expected standard.
Enhanced accessibility
Level AAA contains criteria that significantly improve accessibility but are impractical to meet for all content types. The W3C does not recommend AAA as a blanket requirement for entire sites. AAA criteria are best pursued for high-priority content where enhanced accessibility is possible.
WCAG Versions
From WCAG 2.0 to WCAG 2.2 - what changed?
WCAG has evolved over time. Understanding the differences between versions matters for compliance - different laws reference different versions.
WCAG 2.0 (2008)
The first widely adopted version. Established the four POUR principles and the A/AA/AAA level framework. Still referenced in some older procurement requirements but largely superseded by 2.1.
WCAG 2.1 (2018)
Added 17 new success criteria addressing mobile accessibility, low vision, and cognitive disabilities. Required by AODA and cited in most US ADA court decisions. All WCAG 2.0 criteria are included - 2.1 is a strict superset.
WCAG 2.2 (2023)
The current version. Adds 9 new Level AA and AAA criteria with a focus on keyboard and mobile users, cognitive accessibility, and authentication usability. Introduces Focus Appearance, Target Size, and Dragging Movements requirements. WCAG 2.2 is backwards compatible - meeting 2.2 AA means meeting 2.1 AA.
What's New in WCAG 2.2
The nine new criteria - and why they matter.
WCAG 2.2 introduced criteria that reflect how people actually use the web today - on mobile devices, with limited dexterity, and with cognitive differences.
Focus Not Obscured (AA) - Focused components must not be entirely hidden by sticky headers, cookie banners, or other content.
Focus Not Obscured Enhanced (AAA) - No part of the focused component is obscured by other content.
Focus Appearance (AAA) - Keyboard focus indicators must be large enough and high enough in contrast to be visible.
Dragging Movements (AA) - Any action requiring dragging must have a pointer-based alternative that doesn't require dragging.
Target Size Minimum (AA) - Interactive targets must be at least 24×24 CSS pixels, or have sufficient spacing around them.
Consistent Help (A) - If a help mechanism appears on multiple pages, it must appear in the same relative location across them.
Redundant Entry (A) - Information already entered by a user must not need to be re-entered in the same process.
Accessible Authentication (AA) - Authentication must not require solving cognitive tests or memorizing information unless an accessible alternative is offered.
Accessible Authentication Enhanced (AAA) - Removes the object recognition and personal content exceptions from 3.3.8.
Automated vs. Manual Testing
What can automated WCAG scanning actually detect?
Automated tools — including Diaphone's free WCAG accessibility scanner — reliably catch the failures that appear most often in real-world sites and ADA litigation. But not every WCAG criterion can be evaluated by a machine. Here's an honest breakdown.
Common, measurable failures
Colour contrast — text and UI elements that don't meet the 4.5:1 (normal text) or 3:1 (large text) ratio.
Missing alt text — images with no alternative text attribute present.
Unlabeled form controls — inputs, selects, and textareas with no associated label.
ARIA violations — invalid roles, missing required attributes, incorrect parent/child relationships.
Heading structure — skipped heading levels (e.g. h1 → h3) and missing page headings.
Keyboard focus issues — elements that receive focus but have no visible focus indicator.
Inaccessible names — buttons and links with no discernible text for screen readers.
Document structure — missing page title, missing language attribute, duplicate element IDs.
Table structure — data tables with no headers or incorrect markup.
Judgment-dependent criteria
Alt text quality — a tool can detect a missing alt attribute, but cannot judge whether "image.jpg" or a vague description actually conveys the image's meaning.
Caption accuracy — automated tools can check that captions exist, but not whether they correctly reflect what's being said.
Reading level — whether content is written at an appropriate level for the intended audience.
Error message usefulness — whether form error messages are specific enough to help users recover.
Complete user journeys — whether a checkout flow, multi-step form, or interactive feature is usable end-to-end for keyboard or screen reader users.
Cognitive accessibility — whether content is clear, consistent, and avoids unnecessary complexity.
For teams that ship regularly, WCAG regression testing catches automated-detectable violations the moment they're introduced — before users or auditors find them. Full conformance still requires combining automated scanning with periodic human review.
Who WCAG Helps
1 in 4 adults lives with a disability. WCAG helps all of them - and then some.
WCAG was designed to address the barriers that people with disabilities encounter on the web. But accessible design benefits a much wider audience than that.
Visual Disabilities
Blind users rely on screen readers - software that reads page content aloud. Low-vision users need sufficient colour contrast and the ability to zoom. WCAG ensures content works with these tools.
Motor Disabilities
Users with limited hand mobility may navigate entirely by keyboard, switch controls, or eye-tracking. WCAG requires that everything operable by mouse is also operable without one.
Cognitive Disabilities
Users with dyslexia, ADHD, or memory impairments benefit from clear language, predictable navigation, consistent UI, and forms that don't require memorization. WCAG 2.2 expanded criteria in this area.
Hearing Disabilities
Deaf and hard-of-hearing users need captions for video content and transcripts for audio. WCAG requires that audio-only content has a text alternative.
Mobile Users
Many WCAG criteria - touch target size, zoom support, content that works in both orientations - directly improve mobile usability for everyone, not just users with disabilities.
Aging Population
Age-related changes in vision, hearing, and motor control mean that many seniors benefit from the same accessibility features that assist users with disabilities. The aging population is the fastest-growing online demographic.
Legal Context
WCAG compliance is a legal requirement in more places than most businesses realize.
ADA Title III and WCAG 2.1 AA / 2.2 AA
The Americans with Disabilities Act Title III has been interpreted by courts to require accessible websites. While there is no single federal standard, WCAG 2.1 AA (and increasingly WCAG 2.2 AA) is what courts and the DOJ use as the benchmark. Over 5,000 ADA digital accessibility lawsuits were filed in 2025 - the majority against e-commerce businesses.
AODA requires WCAG 2.1 AA
Ontario's Accessibility for Ontarians with Disabilities Act (AODA) explicitly requires WCAG 2.1 Level AA for public-facing websites and web content. Ontario private-sector organizations with 20 or more employees must file compliance reports by December 31. Penalties for non-compliance reach $100,000 per day. Continuous accessibility monitoring helps you stay compliant between audits.
Federal agencies and their vendors
Section 508 of the Rehabilitation Act requires federal agencies to make their electronic content accessible. The 2018 refresh incorporated WCAG 2.0 AA criteria. Vendors selling to the federal government must meet Section 508 - which in practice means meeting WCAG 2.1 AA or better.
EU accessibility directive
The EU Web Accessibility Directive and European Accessibility Act require public sector websites and many private-sector digital services to meet EN 301 549, which references WCAG 2.1 AA. Requirements are being extended to private-sector companies under the European Accessibility Act.
"Automated WCAG testing catches 30–40% of accessibility issues. Our free WCAG accessibility scanner identifies the most common and legally relevant failures quickly - but full WCAG conformance requires human testing too. We tell you exactly what we check and what automated scanning can't reach. For teams that ship often, WCAG regression testing catches new violations the moment they're introduced." - The Diaphone honesty guarantee
Find out where your site stands against WCAG 2.2 AA - free.
Run a free scan on any URL and get an instant accessibility report against WCAG 2.2 AA, WCAG 2.1 AA, ADA, and AODA criteria. No account required.
Scan My Site Free →