What Is WCAG?
The globally-recognized Web Content Accessibility Guidelines (abbreviated to WCAG, sometimes pronounced “WhuCAG”) are a set of guidelines for making web content more accessible. These guidelines are primarily for people with disabilities and serve as the official standard that countries worldwide look to for digital accessibility.
WCAG is published by the World Wide Web Consortium (W3C), the main international standards organization for the Internet. The W3C is the source of authority on how to achieve digital accessibility. Standards are developed transparently and collaboratively, involving contributors from all over the world.
What Are the WCAG POUR Principles?
WCAG defines four core principles of web accessibility, presented in the acronym POUR:
Perceivable
Information and UI components must be presentable to users in ways they can perceive. Nothing should be invisible to all of a user’s senses.
Operable
UI components and navigation must be operable. Users must be able to operate the interface; it cannot require interaction they cannot perform.
Understandable
Information and the operation of the UI must be understandable. Users must be able to understand both the content and how to use the interface.
Robust
Content must be robust enough to be reliably interpreted by a wide variety of user agents, including assistive technologies like screen readers.
What Are the WCAG Conformance Levels (A, AA, and AAA)?
There are three degrees of compliance a product can aim for. Most legal requirements (including Section 508 and ADA) require Level AA.
| Level | What it means | Required by |
|---|---|---|
| Level A | Minimum baseline. Addresses the most critical barriers. A product that fails Level A is essentially unusable for many people with disabilities. | Baseline for all WCAG compliance |
| Level AA | The standard most organizations target. Addresses the most common barriers without placing an unreasonable burden on content creators. | Section 508, ADA, EN 301 549 (EU), most government contracts |
| Level AAA | The most comprehensive level. Not typically required for entire sites, but can be aspirational or applied to specific content types. | Specialized contexts (e.g., government services for people with disabilities) |
Does WCAG Apply to Mobile Apps and Software?
Unlike standards focused on a single technology, WCAG adapts to different programming languages, browsers, and digital products (including mobile apps, websites, software, and digital content). This technology-agnostic approach is one of its greatest strengths.
The W3C has produced two additional sets of accessibility guidelines alongside WCAG:
- ATAG (Authoring Tool Accessibility Guidelines): making authoring tools accessible, such as Content Management Systems like WordPress and Drupal.
- UAAG (User Agent Accessibility Guidelines): making user agents accessible, such as web browsers, browser extensions, and media players.
Official WCAG Resources
What Is Section 508 and How Does It Relate to WCAG?
Section 508 is a U.S. federal law — specifically an amendment to the Rehabilitation Act of 1973 — that requires federal agencies and organizations that receive federal funding to make their electronic and information technology accessible to people with disabilities. Section 508 is not a separate standard from WCAG: its 2017 refresh incorporated WCAG 2.0 Level AA as the technical benchmark. If your product meets WCAG AA, it meets the technical requirements of Section 508.
What is Section 508?
Section 508 is an amendment to the Rehabilitation Act of 1973. It requires federal agencies and organizations that receive federal funding (such as universities) to make their electronic and information technology (EIT) accessible to people with disabilities.
In practical terms: if your software, website, or digital product is sold to or used by a U.S. federal agency, it must meet Section 508 requirements. The 2017 refresh of Section 508 incorporated WCAG 2.0 Level AA as its technical standard, meaning meeting WCAG 2.0 AA is the baseline for Section 508 compliance.
Section 508 and WCAG are not competing standards. Section 508 references WCAG. If your product meets WCAG 2.0 Level AA, it meets the technical requirements of Section 508. Most teams target WCAG 2.1 AA or 2.2 AA to stay current.
Who Needs to Comply?
Section 508 applies to:
- Federal agencies: all U.S. federal government departments and agencies
- Federal contractors: any organization providing technology products or services to federal agencies
- Federally funded organizations: universities, nonprofits, and other organizations that receive federal grants or funding
If you’re selling SaaS, software, or digital services to any of these entities, a completed VPAT documenting your Section 508 compliance is typically required as part of the procurement process.
What About the ADA?
The Americans with Disabilities Act (ADA) is a separate civil rights law that prohibits discrimination against people with disabilities. While the ADA doesn’t explicitly reference WCAG, courts and the Department of Justice have consistently interpreted it to require accessible websites and digital products for businesses open to the public.
Section 508 applies to federal agencies and their vendors. It has specific technical standards (WCAG 2.0 AA).
ADA applies to private businesses open to the public. It doesn’t specify a technical standard, but WCAG AA is the accepted benchmark in litigation.
Many organizations target WCAG 2.1 AA to satisfy both simultaneously.
Official Section 508 Resources
Need to document your WCAG compliance for a Section 508 procurement? Use the free VPAT Success Criteria Lookup Tool to look up any WCAG criterion with plain-English explanations and VPAT documentation notes.
Frequently Asked Questions
What does WCAG stand for?
WCAG stands for Web Content Accessibility Guidelines. It is the internationally recognized standard for digital accessibility, published by the World Wide Web Consortium (W3C). WCAG defines how to make web content, software, and digital products accessible to people with disabilities.
What is the difference between WCAG Level A, AA, and AAA?
WCAG has three conformance levels. Level A is the minimum baseline — failing it means the product is essentially unusable for many people with disabilities. Level AA is the legal standard required by Section 508, the ADA, and most government contracts worldwide. It covers the most common barriers without placing unreasonable burden on content creators. Level AAA is the most comprehensive level and covers additional edge cases; it is rarely required for entire sites and is not achievable for all content types.
What is the difference between WCAG 2.1 and WCAG 2.2?
WCAG 2.2, published in September 2023, adds 9 new success criteria to the 78 that already existed in WCAG 2.1. The new criteria focus on users with cognitive disabilities, low vision, and limited motor control. Key additions include: Focus Not Obscured (2.4.11) — focused elements must be visible; Dragging Movements (2.5.7) — drag actions need keyboard alternatives; Target Size Minimum (2.5.8) — interactive elements must be at least 24×24px; Redundant Entry (3.3.7) — don't make users re-enter data; and Accessible Authentication (3.3.8) — don't require users to solve puzzles to log in. All WCAG 2.1 criteria still apply in 2.2.
Is WCAG compliance legally required?
WCAG is not itself a law, but it is referenced and enforced through laws that are. Section 508 requires U.S. federal agencies to meet WCAG 2.0 Level AA. The ADA does not cite WCAG explicitly, but courts and the Department of Justice have endorsed WCAG 2.1 Level AA as the accepted standard. In 2024, the DOJ issued a final rule explicitly requiring WCAG 2.1 AA for state and local government digital services under ADA Title II. The EU's EN 301 549 standard references WCAG 2.1 AA for public sector websites and apps.
Does WCAG apply to mobile apps?
Yes. WCAG is intentionally technology-agnostic and applies to websites, web apps, native mobile apps, desktop software, and digital documents. The same success criteria for text alternatives, keyboard operation, and colour contrast apply to iOS and Android apps. Apple's VoiceOver and Google's TalkBack are the primary screen readers for mobile testing. Touch target sizing, gesture alternatives, and orientation support are mobile-specific considerations addressed within WCAG 2.2.
What is Section 508 and how is it different from WCAG?
Section 508 is a U.S. federal law requiring federal agencies and their vendors to make electronic and information technology accessible. WCAG is the technical standard that Section 508 points to — the 2017 Section 508 Refresh adopted WCAG 2.0 Level AA as its technical baseline. So Section 508 is the legal requirement; WCAG is how you meet it technically. The key difference: Section 508 applies specifically to federal procurement contexts, while WCAG is a global standard used by accessibility laws worldwide.
What are the four POUR principles of WCAG?
Every WCAG success criterion maps to one of four principles, forming the acronym POUR: Perceivable — information must be presentable in ways users can perceive (e.g., alt text for images, captions for video); Operable — all functionality must be operable via keyboard and not require interactions users can't perform; Understandable — information and UI operation must be clear and predictable; Robust — content must be interpreted reliably by assistive technologies across different browsers and platforms.