The Web Content Accessibility Guidelines (WCAG) are the international standard for web accessibility, published by the World Wide Web Consortium (W3C). Laws, contracts and audits almost always refer to them, so you need to be able to read them.
This lesson explains how WCAG 2.2 is organised and how to read it without getting lost.
Versions
WCAG has several versions. Each one is backwards compatible: if you meet WCAG 2.2, you also meet 2.1 and 2.0.
| Version | Published | What it added |
|---|---|---|
| WCAG 2.0 | 2008 | The core principles and most success criteria |
| WCAG 2.1 | 2018 | Mobile, low vision and cognitive criteria, such as Reflow and Non-text Contrast |
| WCAG 2.2 | 2023 | Focus visibility, target size, dragging alternatives and accessible authentication |
WCAG 2.2 also made 4.1.1 Parsing obsolete, because modern browsers and assistive technologies handle markup errors consistently.
A very different future standard, WCAG 3, is in development. It is a draft, not a requirement. Use WCAG 2.2 for current work.
The structure: four layers
WCAG is organised from general to specific.
- Principles: four broad ideas, known as POUR.
- Guidelines: 13 goals under the principles, such as 1.4 Distinguishable.
- Success criteria: testable statements, each with a number, a name and a level, such as 1.4.3 Contrast (Minimum), level AA.
- Techniques: advice on ways to meet each criterion. Techniques are informative, not required.
Only the success criteria are what you conform to. Everything else is there to help you understand and meet them.
The POUR principles
| Principle | Question to ask | Example success criteria |
|---|---|---|
| Perceivable | Can everyone perceive the content, whatever senses they use? | 1.1.1 Non-text Content, 1.2.2 Captions (Prerecorded), 1.4.3 Contrast (Minimum) |
| Operable | Can everyone operate the interface, whatever input they use? | 2.1.1 Keyboard, 2.4.7 Focus Visible, 2.5.8 Target Size (Minimum) |
| Understandable | Can everyone understand the content and how the interface behaves? | 3.1.1 Language of Page, 3.3.1 Error Identification |
| Robust | Does it work with current and future browsers and assistive technologies? | 4.1.2 Name, Role, Value, 4.1.3 Status Messages |
The number of every success criterion starts with its principle. Anything beginning 2. is about operating the interface.
Conformance levels
Each success criterion has a level.
- Level A: the minimum. Failing these blocks some people completely, for example a control that cannot be reached with a keyboard.
- Level AA: removes significant barriers for many more people, for example sufficient text contrast. This is the level most laws and policies require.
- Level AAA: the highest level. W3C does not recommend requiring AAA for entire sites, because some content cannot meet every AAA criterion. Meet the AAA criteria that are relevant to your users where you can.
To conform at level AA, a page must meet all level A and level AA success criteria. There is no partial conformance score. One failing criterion means the page does not conform at that level.
Conformance also applies to complete pages and complete processes. A checkout does not conform if the payment step fails, even if every other step passes.
Reading a success criterion
Here is 2.4.7 Focus Visible, level AA, as written in WCAG 2.2:
2.4.7 Focus Visible (Level AA)
Any keyboard operable user interface has a mode of operation
where the keyboard focus indicator is visible.Read it in three steps.
- Who does it affect? Keyboard users, who need to see where they are on the page.
- What must be true? When you tab through the page, something always shows which element has focus.
- How would I test it? Tab through every interactive element and check that each one shows a visible indicator.
Some wording is precise on purpose. Words such as "programmatically determined", "user interface component" and "large scale text" are defined in the WCAG glossary. When a criterion seems ambiguous, look up the defined terms.
The supporting documents
The normative standard is short and dense. W3C publishes companion documents that make it practical.
- Understanding documents explain the intent of each criterion, who benefits, and examples. Start here when a criterion is unclear.
- How to Meet WCAG (Quick Reference) lists every criterion with filters for level and technology.
- Techniques describe sufficient techniques (ways to pass) and common failures (ways to fail), with test procedures.
For example, the Understanding page for 1.4.3 explains that the 4.5:1 ratio allows for the reduced contrast sensitivity that comes with moderately low vision and with ageing.
New in WCAG 2.2
These are the success criteria added in 2.2. You will meet most of them later in the course.
| Criterion | Level | In short |
|---|---|---|
| 2.4.11 Focus Not Obscured (Minimum) | AA | The focused element is not completely hidden by sticky headers or banners |
| 2.4.12 Focus Not Obscured (Enhanced) | AAA | No part of the focused element is hidden |
| 2.4.13 Focus Appearance | AAA | Focus indicators are large and contrasting enough |
| 2.5.7 Dragging Movements | AA | Anything done by dragging can also be done with single clicks or taps |
| 2.5.8 Target Size (Minimum) | AA | Pointer targets are at least 24 by 24 CSS pixels, or have enough spacing |
| 3.2.6 Consistent Help | A | Help links and contact details appear in the same place across pages |
| 3.3.7 Redundant Entry | A | Users are not asked for the same information twice in one process |
| 3.3.8 Accessible Authentication (Minimum) | AA | Logging in does not depend on a cognitive test such as remembering or transcribing, unless help is provided |
| 3.3.9 Accessible Authentication (Enhanced) | AAA | A stricter version of 3.3.8 |
Meeting WCAG is the floor, not the ceiling. A site can pass every criterion and still be hard to use. Test with real people, including disabled people, whenever you can.
Summary
- WCAG is the W3C standard that laws and audits refer to; use version 2.2.
- It is organised as principles, guidelines, success criteria and techniques.
- POUR: content must be Perceivable, Operable, Understandable and Robust.
- Level AA means meeting every A and AA criterion; it is the usual legal target.
- Read a criterion by asking who it affects, what must be true and how you would test it.
- The Understanding documents explain the intent behind each criterion.
In the next lesson you will meet the first success criterion in WCAG, 1.1.1 Non-text Content, by writing alt text.