A11ying with Sanna - Web Content Accessibility Guidelines a guide to the accessibility requirements
1 Perceivable

1.4.4 Resize Text

Conformance level: AA
Criterion released in WCAG version: 2.0

Official description of the success criterion

Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality.

What to do?

Allow text to be resized up to 200% without loss of content or functionality.

Why is it important?

Supports users with low vision.

Common pitfalls

There are a lot of different types of issues when it comes to text-only zooming. For example:

  • Using pixel widths and heights on elements.
  • Incorrect use of viewport units.
  • Not using hyphenation, which causes longer words to be clipped.

How to test for it?

Use text-only zoom and check the content. At least Safari and Firefox have text-only zooming available by default.

Automated tools can detect some of these occasionally but a lot of the testing must be done manually.

More about this criterion elsewhere