In anticipation of "ugh, designers are ruining the web custom fonts", I'm glad that variable fonts are starting to percolate out. https://developers.google.com/web/fundamentals/design-and-ux... Less overall file size, less HTTP requests. Combine that with preloading and font-display, we're getting to the point where webfonts aren't a giant bandwidth suck. https://developers.google.com/web/fundamentals/performance/o..…
I remember when Adobe launched Multiple Master fonts [1] in 1992 (same concept)... and then killed them in 1999 because not enough people were using them.
I'll be fascinated to see if there's actually demand for it this time around. I personally have had tons of times I've wanted a semibold where none existed, or something halfway between regular and condensed.
But I'm not convinced they're going to save bandwidth for most sites. After all, they incorporate two sets of font outlines along each dimension instead of one, right? And you rarely see a webpage that uses three variations of a font along a single dimension (e.g. sans-serif regular, semibold and bold). A "third" font and beyond is more often a different style (italics) or typeface (serif) entirely. So I don't see the savings in most cases...