What Is WCAG and What Accessibility Standard Should UK Websites Meet?

WCAG stands for Web Content Accessibility Guidelines. Published by the World Wide Web Consortium (W3C), WCAG is the internationally recognised standard that defines what makes a website accessible to people with disabilities. It underpins accessibility law in many countries, including the UK’s Public Sector Bodies Accessibility Regulations.

Understanding WCAG — what the different levels mean, and which version applies to you — is the first step to building a website that genuinely works for everyone.

How WCAG Is Organised

WCAG is built around four core principles, often abbreviated as POUR: Perceivable, Operable, Understandable, and Robust. A website is accessible only if it satisfies all four: content must be perceivable by all users (including those using screen readers), the interface must be operable without a mouse, the content must be understandable, and the site must be robust enough to work reliably with assistive technologies.

Within those four principles are thirteen guidelines, and beneath those guidelines are specific testable success criteria — the individual pass/fail checks that determine whether a site meets the standard. WCAG 2.1 contains 78 success criteria; WCAG 2.2 adds nine new ones.

Each success criterion is assigned one of three conformance levels: A (minimum), AA (standard), or AAA (enhanced). Level A covers the most critical barriers — issues that make a site completely unusable for some users. Level AA includes the majority of practical accessibility requirements. Level AAA is the most demanding and is often considered aspirational rather than obligatory.

Which Version of WCAG Should UK Websites Follow?

WCAG 2.1 was published in 2018 and is currently the version referenced in UK law. The Public Sector Bodies Accessibility Regulations 2018 require public sector websites and apps to meet WCAG 2.1 Level AA. WCAG 2.2, published in October 2023, is the most current version and adds new criteria focused on mobile usability and cognitive accessibility.

For public sector organisations, the UK government has signalled that WCAG 2.2 AA compliance will become the expected standard, though the formal legal requirement is still WCAG 2.1 AA at time of writing. For private sector businesses, there is no direct statutory requirement to meet a specific WCAG level, but demonstrating WCAG 2.1 or 2.2 AA compliance is the most credible way to show that reasonable adjustments have been made under the Equality Act 2010.

Practically speaking, if you’re commissioning a new website in 2024 or later, ask your web designer to build to WCAG 2.2 Level AA. This future-proofs your site and represents genuine best practice.

Key WCAG Success Criteria to Prioritise

Rather than attempting to address all 78+ criteria at once, focus first on the ones most likely to create significant barriers: sufficient colour contrast (1.4.3), text alternatives for non-text content such as images (1.1.1), keyboard accessibility (2.1.1), descriptive page titles and headings (2.4.2, 2.4.6), visible focus indicators (2.4.7), and error identification and suggestions in forms (3.3.1, 3.3.3).

These criteria address the most common and impactful barriers. Fixing them typically involves a combination of content changes (adding alt text, improving link wording), design changes (increasing contrast, improving focus styles), and development changes (ensuring keyboard operability, using semantic HTML).

Use the official W3C quick reference — “How to Meet WCAG” — as your go-to resource. It allows you to filter by conformance level and guideline and provides both techniques and common failures for each criterion.