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Reflow @ 320px Previewer

WCAG 1.4.10 requires content to reflow at 320 CSS pixels without two-dimensional scrolling. This tool renders your markup at exactly 320px, detects horizontal overflow, and pinpoints the elements forcing it.

Web Accessibility Local processing Your code stays in your browser. Nothing is uploaded.

Tool interface

Introduction

Users with low vision zoom in; the layout must then reflow to a narrow column without horizontal panning. Testing at 320px catches the fixed-width culprits early.

How it works

  • Renders desktop and 320px previews in sandboxed iframes.
  • Compares scrollWidth vs clientWidth at 320px.
  • Isolates outermost elements whose right edge exceeds the boundary.
  • Highlights them and reports the computed properties causing overflow.

Privacy

All rendering and measurement is local. No upload, no account, no API key.

Limitations

  • Sandboxed preview blocks scripts in your snippet.
  • Cannot judge 1.4.10 exemptions (maps, tables) — that's a human decision.

FAQ

Why 320 pixels?

WCAG 1.4.10 defines reflow at a width equivalent to 320 CSS pixels (400% zoom at 1280px).

Is my code uploaded?

No. Everything runs locally.

Related tools

Version and changelog

  • Version: 1.0.0
  • Last updated: August 12, 2026
  • Changelog: Initial production release.