Text Spacing
No loss of content or functionality occurs when line height is set to at least 1.5 times the font size, spacing following paragraphs to at least 2 times the font size, letter spacing to at least 0.12 times the font size, and word spacing to at least 0.16 times the font size.
In plain language
If someone increases the spacing between lines, paragraphs, letters, or words (using a browser extension or their own settings), the page shouldn't break, cut off text, or lose functionality.
Why it matters
People with dyslexia and other reading disabilities often rely on extra spacing to read comfortably. If a site can't handle that adjustment, it becomes literally unreadable for them, even though the same site works fine for everyone else.
In practice
Fails this criterion
A heading has a fixed-height box, so when line spacing is increased, the bottom of the text gets clipped and becomes unreadable.
Meets this criterion
The same heading sits in a flexible container that grows to fit the text, so increased spacing just makes the box taller — nothing is cut off or hidden.
Test it yourself
Use a browser extension (or bookmarklet) that applies the WCAG text-spacing values (line height 1.5x, paragraph spacing 2x, letter spacing 0.12x, word spacing 0.16x) to the page. Check whether any text gets cut off, overlaps, or becomes unusable.