How single-file variable fonts replace dozens of separate weight files using design axes (wght, wdth, slnt).
What Is an OpenType Variable Font?
Traditionally, if you needed Thin, Light, Regular, Medium, Bold, and ExtraBold, you had to load six separate font files. Variable fonts package continuous interpolations of all weights and widths into a single file, controlled via CSS properties like `font-weight: 540` and `font-variation-settings`.