WCAG 1.4.10 — Reflow, explained with examples

Why this criterion exists

Users zoom in heavily and small-screen users need content to wrap. Fixed widths fail this regularly.

If you only remember one thing: content must reflow to a 320 css pixel width (the equivalent of 400% zoom on a 1280px viewport) without requiring horizontal scrolling for the primary reading direction. Everything else on this page is detail.

Who feels it when this fails

Accessibility criteria sometimes feel abstract until you see who pays the cost when a site ignores them. Reflow affects:

• Low-vision users

• Mobile users

How sites typically fail it

These are the patterns we see week after week. None are intentional — they are accidents of how teams build interfaces under deadline. Knowing the failure modes is the fastest path to writing them out of your component library.

• Tables and code blocks creating horizontal scroll on mobile

How to test for it

• Resize the browser to 320px wide; no horizontal scroll allowed.

A code fix you can copy

Constrain the scroll to the data table, not the page.

.table { min-width: 800px; }

@media (max-width: 600px) {
  .table { display: block; overflow-x: auto; }
}