Web development and performance
What is WCAG?
WCAG is the international standard for web accessibility, organised into levels A, AA and AAA. AA is the level referenced by most legislation, including the European Accessibility Act and public-sector rules in the UK, US and Canada.
Also called: Web Content Accessibility Guidelines · WCAG 2.2 AA
The four principles
- Perceivable
- Users can perceive the content — text alternatives, contrast, captions.
- Operable
- Users can operate it — keyboard access, enough time, no seizure triggers.
- Understandable
- It behaves predictably, and errors are explained.
- Robust
- It works with assistive technology, now and as that technology changes.
The criteria most commonly failed
- Colour contrast below 4.5:1 for body text and 3:1 for interface elements
- Focus that is invisible or removed with an outline: none
- Images with missing or meaningless alternative text
- Form fields labelled by placeholder text alone
- Animation running over five seconds with no pause control — a Level A failure
The commercial reason, not just the legal one
Accessibility work overlaps almost entirely with usability and technical SEO: real labels, real elements, readable contrast, working keyboard navigation. Doing it during a build costs almost nothing; retrofitting it after a complaint costs several times more.
Where this is covered in depth
A definition can only go so far. The 35 types of SEO, explained without the padding covers this properly — 6 minutes, free, no email required.
Who wrote this
Anas Bin Masud builds e-commerce sites and does technical SEO for businesses in the UK, Canada and Pakistan. These definitions come from client work rather than from a content brief — where an entry describes a mistake, it is usually one found on a real site. More about how I work.