What is WCAG?
The Web Content Accessibility Guidelines (WCAG) are the international standard for web accessibility, published by the World Wide Web Consortium (W3C) through its Web Accessibility Initiative (WAI). They define how to make web content more accessible to people with disabilities.
WCAG covers a wide range of recommendations for making web content more accessible to people who are blind or have low vision, deaf or hard of hearing, have limited movement, have speech disabilities, have photosensitivity, have learning or cognitive disabilities, or some combination of these.
"Following these guidelines will make content accessible to a wider range of people with disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement, speech disabilities, photosensitivity, and combinations of these."
— W3C Web Accessibility InitiativeWCAG version history
WCAG has evolved through several versions. WCAG 2.2 (published October 2023) is the current recommended standard and the one WebPossum tests against.
The 4 POUR principles
WCAG is built around four core principles, often called POUR. Every success criterion in WCAG falls under one of these four categories.
Perceivable
Information and interface components must be presentable to users in ways they can perceive.
Operable
User interface components and navigation must be operable by all users.
Understandable
Information and the operation of the interface must be understandable.
Robust
Content must be robust enough to be reliably interpreted by assistive technologies.
Conformance levels: A, AA, and AAA
WCAG organizes its success criteria into three levels of conformance. Most organizations and legal frameworks target Level AA as their standard.
Basic accessibility
The most basic requirements. Failing Level A makes content completely inaccessible to some users. This is the floor, not the goal.
30 success criteria · Examples: alt text, no keyboard traps, page title
The internationally required level
Required by ADA (US), AODA (Canada), EN 301 549 (EU), and the Equality Act (UK). Covers the most common and impactful barriers.
20 additional criteria on top of Level A
The highest standard
Not required by any current law for entire websites. It is not possible to satisfy all AAA criteria for all content.
28 additional criteria · Enhanced contrast, sign language, no timing
What is new in WCAG 2.2
WCAG 2.2 (October 2023) added 9 new success criteria compared to WCAG 2.1. These focus primarily on cognitive accessibility, mobile usability, and focus visibility.
Focus Not Obscured (Minimum)
2.4.11 — AAWhen a UI component receives keyboard focus, it must not be entirely hidden by sticky headers or overlays.
Focus Not Obscured (Enhanced)
2.4.12 — AAANo part of the focused element is hidden by author-created content. Stricter version of 2.4.11.
Focus Appearance
2.4.13 — AAAThe keyboard focus indicator must have a minimum area and sufficient contrast ratio of at least 3:1.
Dragging Movements
2.5.7 — AAAll functionality that uses dragging can also be achieved with a single pointer action.
Target Size (Minimum)
2.5.8 — AAThe size of pointer input targets is at least 24×24 CSS pixels. Helps users with motor disabilities.
Consistent Help
3.2.6 — AHelp mechanisms must appear in the same relative order when repeated across multiple pages.
Redundant Entry
3.3.7 — AInformation previously entered must be auto-populated or available for selection in multi-step forms.
Accessible Authentication (Minimum)
3.3.8 — AAA cognitive function test must not be required in authentication unless an alternative is provided.
Accessible Authentication (Enhanced)
3.3.9 — AAANo cognitive function test is required in any authentication step. No exceptions.
Legal requirements worldwide
Web accessibility is a legal requirement in most jurisdictions. Failing to comply exposes your organization to lawsuits, fines, and reputational damage.
Even where laws don't explicitly mandate WCAG, courts in the US, UK, and Australia have accepted WCAG Level AA as the standard of reasonable accommodation in discrimination cases.
Who WCAG protects
Accessibility affects a broader range of users than most people assume. WCAG criteria address these disability categories:
Blindness, low vision, color blindness. Screen readers, magnification, and high-contrast modes must work correctly.
Deafness and hard of hearing. Audio content must have captions or transcripts.
Limited fine motor control, tremors, paralysis. Keyboard navigation and sufficient target sizes are critical.
Dyslexia, ADHD, memory impairments. Clear language, consistent navigation, and error prevention help.
Users who cannot use voice interfaces must have non-voice alternatives available.
Photosensitive epilepsy. Content must not flash more than 3 times per second.
Accessibility also benefits users without permanent disabilities: people using a phone in sunlight, people in noisy environments, people with a broken arm, and elderly users.
Quick WCAG 2.2 AA checklist
The most common WCAG 2.2 Level AA failures found on real websites. WebPossum automatically tests all of these.