• Success Criterion 1.4.10
  • Conformance level AA

Nested Scroll Area Requiring Scrolling in Both Directions

1.4.10 — Reflow

Scenario

Setting

A customer-support live-chat widget

What’s wrong

Zoom traps: content requiring both directions of scroll inside nested scroll containers.

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 and scroll within nested scroll containers: if reaching content requires scrolling both horizontally and vertically inside a nested box, 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 a customer-support live-chat widget, this barrier is gone for low-vision users at high zoom and people reading on narrow mobile viewports — they reach the same outcome without extra effort.

Who is affected

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

Learn more

Related scenarios