What Is WCAG and Which Level Should Your Website Meet?

WCAG stands for Web Content Accessibility Guidelines. It’s an internationally recognised set of guidelines published by the World Wide Web Consortium (W3C) that defines what it means for a website or web application to be accessible to people with disabilities.

WCAG is the primary standard referenced in UK and EU accessibility legislation, and it’s the benchmark most web accessibility auditors use when assessing a site. Understanding what WCAG is and what its different conformance levels mean will help you make informed decisions about your website.

The Four WCAG Principles

WCAG is organised around four core principles, often summarised by the acronym POUR: Perceivable, Operable, Understandable, and Robust.

Perceivable means that all information and user interface components must be presentable to users in ways they can perceive — for example, providing text alternatives for images. Operable means all interface components and navigation must be operable — for example, being fully usable with a keyboard. Understandable means content and operation must be understandable — for example, form errors must be clearly explained. Robust means content must be robust enough to be reliably interpreted by a wide variety of user agents, including assistive technologies like screen readers.

Under each principle sit a series of testable success criteria. Meeting these criteria at a given level determines your level of conformance.

WCAG Conformance Levels: A, AA, and AAA

WCAG has three levels of conformance: Level A (minimum), Level AA (standard), and Level AAA (enhanced). Level A covers the most fundamental accessibility requirements — without these, some users simply cannot access the content at all. Level AA adds a broader set of requirements that address the most significant barriers for most disabled users. Level AAA is the most stringent and is not required (or always achievable) for general websites.

The current version most widely used in UK and European legal contexts is WCAG 2.1. WCAG 2.2 was published in October 2023 and adds nine new success criteria, mainly focused on cognitive accessibility and mobile users. WCAG 3.0 is in development and will introduce a fundamentally different scoring model, though it is unlikely to become a legal standard for several years.

Which Level Should Your Website Target?

WCAG 2.1 Level AA is the standard required by UK public sector regulations and referenced in most accessibility legal guidance. For private sector businesses in the UK, meeting WCAG 2.1 Level AA represents a solid and defensible commitment to accessibility under the Equality Act 2010.

If you’re building a new website, aim to design and develop to WCAG 2.1 Level AA from the outset — it’s significantly cheaper and easier to build accessibility in than to retrofit it later. If you have an existing site, an accessibility audit will identify which criteria you currently fail, and you can prioritise remediation starting with Level A failures before moving on to Level AA.

For most UK businesses, achieving Level AA conformance is realistic and meaningful. Level AAA conformance is worth pursuing in specific contexts — for example, if your audience includes a high proportion of disabled users or if you operate in the public or healthcare sector.