It's still saving probably a single byte in this example

.a { color: red }

.b { color: red }

Also it saves on parsing time I suppose. And less to zip and unzip.

The type of thing I'd add to a projects deployment stage and never touch again unless it causes an issue.

Yeah, I mean this is not purely about reducing space at least from my point of view I wanted to better organize my CSS and I reduced duplication so that the overall structure would be clear to me and for what I wanted to do it would be easier to maintain in modify. A more ‘normalized’ (in the language of relational databases) CSS haha! :)

Still takes time to parse and apply the styles though.

CSS is probably a much smaller concern than JS but in the world of 5G networks and fast WiFi I feel like we’re nearing a world where device CPU can be a bigger bottleneck than bandwidth at times.