A new font specification that can significantly reduce font file sizes
In this article, you'll discover what variable fonts are, the benefits they offer, and how to use them in your work. First, review how typography works on the web, and what innovations variable fonts bring.
Browser compatibility
As of May 2020 variable fonts are supported in most browsers. See Can I use variable fonts? and Fallbacks.
Introduction
The terms font and typeface are often used interchangeably by developers. However there is a difference: A typeface is the underlying visual design that can exist in many different typesetting technologies, and a font is one of these implementations, in a digital file format. In other words, a typeface is what you see, and the font is what you use.
Another concept that is often overlooked is the distinction between a style, and a family. A style is a single and specific typeface, such as Bold Italic, and a family is the complete set of styles.
Before variable fonts, each style was implemented as a separate font file. With variable fonts, all styles can be contained in a single file.