2026
4 featuresThe rcap CSS length unit is a font-relative length equal to the value of the cap unit on the root element. Cap-height is approximately equal to the height of a capital Latin letter.
The rch CSS length unit is a font-relative length equal to the value of the ch unit on the root element. ch length is based on the width of the zero (0) character.
The rex CSS length unit is a font-relative length that is equal to the x-height of the root element.
2023
3 featuresThe rlh CSS length unit is a font-relative length relative to the line height of root element.
2022
1 features2020
1 features2017
1 featuresThe vw, vh, vmin, and vmax CSS viewport units are relative to the size of the viewport, and are used to size elements in relation to the viewport's dimensions.
2015
4 featuresThe ch CSS length unit is a font-relative length based on the width of the zero (0) character.
The em CSS length unit is a font-relative length equal to the specified font size. In an element with a 2 inch font, 1em equals 2 inches.
The ex CSS length unit is a font-relative length equal to the used x-height of the first available font. X-height is often equal to the height of the lowercase x.