What Is Variable Font?
A variable font is a single file that contains a continuous range of styles along one or more axes — weight, width, slant, optical size — instead of separate files per style. One variable font can replace a dozen static weights, cutting load time on the web while giving designers fine-grained control.
Axes are defined by the designer. Common ones are weight (wght), width (wdth), slant (slnt), and optical size (opsz). You can set any value along an axis, not just preset stops.
On the web, variable fonts shrink page weight dramatically and enable smooth animation between weights, which is why they are increasingly the default for performance-conscious sites.