What is the WordPress theme `theme.json` v3 schema’s `fluid` typography feature and how does it work at the CSS level?

Question

WordPress Expert — Hard

What is the WordPress theme `theme.json` v3 schema’s `fluid` typography feature and how does it work at the CSS level?

Accepted Answer

The `theme.json` v3 schema's fluid typography feature generates CSS clamp() values for font sizes that smoothly scale between a minimum and maximum value based on viewport width. This eliminates font size jumps at breakpoints and is resolved by the block editor using the typography.fluid settings in theme.json.