Web Accessibility: What It Is and Why It Matters for SEO

1 What is web accessibility?

Web accessibility means making sure your website can be used by everyone — including people who are blind or visually impaired, deaf, have motor difficulties, or use assistive technology like screen readers. Approximately 1 in 5 people in the UK have some form of disability.

2 How accessibility affects SEO

Google's crawler behaves similarly to a screen reader — it reads text, follows links, and processes HTML structure. Many accessibility fixes directly improve how Google reads your pages:

3 How to run an accessibility audit

1. 1 Open the Accessibility Checker Go to performance-tools.html#accessibility and enter the URL of a page you want to audit.
2. 2 Review Level A violations first Level A issues are the most critical — these are failures that completely block some users from using your page. Fix these before anything else.
3. 3 Check contrast ratios Text must have a contrast ratio of at least 4.5:1 against its background for normal text, and 3:1 for large text. The tool shows the exact ratio for any failing elements.
4. 4 Fix missing alt text on images Every image that conveys information needs an alt attribute describing what it shows. Decorative images should have alt="" — an empty alt attribute — so screen readers skip them.

4 The most common accessibility issues

1. ⚠ Images without alt text Add alt="description of image" to every img tag. For example: <img src="team.jpg" alt="Our team of five developers in the office">
2. ⚠ Form inputs without labels Every input needs a label. Add <label for="email">Email address</label> before each input, with a matching id on the input itself.
3. ⚠ Low colour contrast Grey text on a white background often fails. Use a contrast checker or the Accessibility Checker tool to find failing elements, then darken the text colour until it passes.