Success Criterion 1.4.10
Conformance level AA

Vertical Content That Forces Horizontal Scrolling at 320px

1.4.10 — Reflow

Scenario

Setting

An online clothing store's product listing page

What’s wrong

Horizontal scrolling required for vertically-scrolling content at 320 CSS px (400% zoom on 1280) — fixed-width layouts.

Example

.layout { width: 1200px; }

Why it matters

Low-vision users at high zoom and people reading on narrow mobile viewports.

How to test

Set the viewport to 320px wide: if a horizontal scrollbar appears for content that should scroll only vertically, it fails.

How to fix

At 320 CSS px width (400% zoom on a 1280px desktop), content must reflow into one column with only vertical scrolling and nothing missing or unreachable. .layout { max-width: 1200px; width: 100%; } Content must reflow into one column at 320px wide with no horizontal scrolling and nothing missing.

Outcome

On an online clothing store's product listing page, this barrier is gone for low-vision users at high zoom and people reading on narrow mobile viewports — they can finish what they came here to do.

Who is affected