Success Criterion 1.4.10
Conformance level AA

1.4.10 · Reflow

Lesson overview · Reflow

In plain language

At 320px width (400% zoom on desktop) content must reflow into one column with no horizontal scrolling and nothing missing.

Who it affects

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

How to check

Set the viewport to 320px wide (or zoom desktop to 400%): scroll only vertically; confirm no content or controls have vanished.

Common misconception

Having a “mobile view” isn't the same as passing reflow. This rule is tested by zooming a desktop browser to 400%, not by shrinking the viewport, and the two don't always behave the same.

Learn more

Understanding Understanding this success criterion (opens in a new tab)

Scenarios in this lesson

Content or Controls That Vanish Entirely When the Page Reflows
Vertical Content That Forces Horizontal Scrolling at 320px
Fixed-Width Container Forcing Scrolling in Two Directions
Overlapping Content When the Page Is Zoomed to 400%
Sticky Bars That Eat Up Most of a 320px Mobile Screen
Desktop Breakpoint That Never Switches to Mobile Layout
Long Unbroken Text or URL That Forces Horizontal Scrolling
Desktop Hover Menu That Becomes Unreachable on Small Screens
Form Labels or Inputs That Clip at Narrow Screen Widths
Modal Dialog Wider Than the Viewport With Unreachable Buttons
Data-Table Reflow Exception Wrongly Applied to a Layout Table
Carousel Slide Content Cut Off With No Way to Reach It
Nested Scroll Area Requiring Scrolling in Both Directions
Floating Chat Widget Blocking Content at Mobile Width