Ann takes a look at the Roboto Variable Font compared against loading static versions of the Font to see which has the better performance. As with most things, it depends is really the answer, but this should make you think twice before automatically reaching for a variable font (and it helps you understand what you should be thinking twice about when doing so).
On the other hand, a variable font file is huge, precisely because it contains all the variations. The Roboto Variable Font, for instance, is 3.36MB in TTF format, while a static Roboto font variant is around 165–175KB in TTF format. Even if we need to use all 12 variants, that’s still only around 2MB in total.
Ultimately, the performance trade-off of variable fonts depends on how these two metrics — the number of HTTP requests and the total size of font files — balance each other out.An excerpt from Variable fonts: Is the performance trade-off worth it?