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AccessibilityCraft conventionFoundational

Text Resize

Text must scale to 200 percent without breaking, which means never sizing type in absolute units.

Definition

WCAG 1.4.4 requires text to be resizable up to 200 percent without loss of content or functionality. On mobile platforms, the operating system font size setting must also be respected.

Craft convention. True because the industry converged on it. Breaking it costs familiarity, not correctness.

On this page
  1. Definition
  2. Requirements
  3. Sources
  4. Continue from here

Requirements

  • Size text in rem or em, never in px, so the user's browser setting applies.
  • Do not set a font size on the html element in pixels, which overrides the user preference.
  • Avoid fixed-height containers around text.
  • Include a rem term in any clamp expression, or viewport-based sizing will ignore zoom entirely.
  • On mobile, respect the platform's dynamic type or font scale setting.
  • Test at 200 percent text-only zoom, which is different from full page zoom and breaks more layouts.

Sources

Where a source establishes something narrower than the popular reading of it, the note says so.

Continue from here

Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.

Applies when you are designing

A Mobile App

Check your work

Review passes that test whether this was done properly.

Related concept

Connected closely enough to change how you apply this.