Accessibility is usability with the edge cases included

Accessibility gets treated as a specialist legal topic. In practice, most of it is a short list of things that also make a site easier to use for people with perfect vision on a good connection.

The overlap

• Text with real contrast helps people with low vision, and everyone outdoors in sunlight.
• Captions help deaf viewers, and everyone watching without sound in public.
• Big, well-spaced tap targets help people with tremors, and everyone on a bumpy bus.
• Clear labels on form fields help screen readers, and everyone filling in a form quickly.

The cheapest wins

Write meaningful alt text on images that carry information. Do not rely on colour alone to signal something. Make sure the site can be operated by keyboard. Keep the text large enough to read without pinching.

You do not need an audit to start. You need to stop introducing the obvious problems, and to fix the ones that already exist when you find them.