You wrote end-to-end tests. They were green, you felt good, you shipped. Six weeks later half of them are red, nothing is actually broken, and the team has quietly agreed to stop looking at the results. This is how most test suites die: not because the app got worse, but because the tests got too expensive to keep alive. The failure is not laziness. It is the way the tests were written.

Accessibility can feel like an endless spec, but in practice a small number of issues account for the large majority of what any scan finds. Fix these and you clear most of the gap to WCAG 2.1 AA. Here is the short list, what each one means, who it hurts, and how to fix it.

Your signup flow is the one path every customer has to complete, and it is usually the least tested. You built it early, it worked, and you moved on. Meanwhile it quietly depends on your auth provider, your email service, a database write, a redirect, and a pile of client-side JavaScript, any of which can break without throwing an obvious error. When signup breaks, you do not get a bug report. You get silence, and a conversion number that drifts down for reasons nobody can explain.

WCAG, the Web Content Accessibility Guidelines, is the standard that defines what it means for a website to be usable by people with disabilities. If you have ever wondered whether your SaaS is "accessible enough," WCAG is the yardstick almost everyone (including courts and procurement teams) actually measures against.

Here is what it is, how it is structured, and why it is worth caring about even before anyone forces you to.