Viewport-relative units (such asvh andvw) are commonly used among UI design for sizing and spacing of elements.

With the new container queries spec, authors will want to use such units as container-height (ch) and container-width (cw) for container-based sizing.

An example is usingcw units insrcset similarly to how one would usevw units insrcset. Percentages would not work in that instance, as the value needs to be absolute or relative length.

Edit:ch would not work as a unit name due to the existingch (character) unit