I had the same problem and had some luck cleaning things up by enabling "calculate all sizes" in Finder, which will show you the total directory size, and makes it a bit easier to look for where the big stuff is hiding. You'll also want to make sure to look through hidden directories like ~/Library; I found a bunch of Docker-related stuff in there which turned out to be where a lot of my disk space went.
You can enable "calculate all sizes" in Finder with Cmd+J. I think it only works in list view however.
I’d recommend GrandPerspective:[1] it’s really good at displaying this sort of thing, has been around for over two decades, and the developer has managed to keep it to <5MB which is perfect when you’re running very low on space.
I use GP, would recommend as well; it generates great color codes tree maps of your storage. Once you get used to navigating it that way, you won’t go back.
Something like https://dev.yorhel.nl/ncdu with ("brew install ncdu") is great if you are okay with the command line. It's very annoying to drill down in the Finder especially if it's hidden directories.
in a similar vein if you are looking for a nice GUI, daisydisk is great: https://daisydiskapp.com one time $10 payment
A ton of thanks. This "hack" allowed to finally see some stuff that was eating up a lot of my space and was showing up as "System Data". It turned out the Podman virtual machine on my MacBook had eaten up more 100GB!
Also DaisyDisk! Beautiful app. Perfect for discovering this kind of thing.
You can also just use du -hs, eg. to show the size of all subdirectories under ~/Library/Caches/ do:
du -hs ~/Library/Caches/*