Application Support was 14.3 GB, and half of it was one browser

Open ~/Library/Application Support on a Mac that has been in use for a year and Finder shows a long list of folders with no sizes. It is one of the largest folders in your Library, and nothing in macOS tells you so.

What was in it

The top two folders are 75 percent of the total. That shape is typical: Application Support is not full of small forgotten things, it is full of a few apps built on a browser engine, each keeping a whole browser profile's worth of data.

Measure yours

du -sh ~/Library/Application\ Support/* 2>/dev/null | sort -h | tail -15

Run it once without Full Disk Access and some folders will read as tiny. macOS hides the contents of a few from Terminal until you grant it, so a small number is not always a true one.

What is safe to remove

The Chrome folder is the clearest example of the last row. It is large, but it is your bookmarks, saved passwords and site logins, so deleting it is signing out of everything. The useful move is removing profiles you no longer use, which is covered in Chrome taking up space.

Finding folders whose app is gone

Folder names are either the app's name or its bundle identifier, like com.isaacmarovitz.Whisky. This asks macOS whether anything installed still owns each identifier:

cd ~/Library/Application\ Support
for d in com.* dev.* org.* io.*; do
  [ -d "$d" ] || continue
  mdfind "kMDItemCFBundleIdentifier == '$d'" | grep -q . || echo "no app: $d  $(du -sh "$d" | cut -f1)"
done

It is a hint rather than proof. An app's helper can use an identifier that is not its own, and an app that is not indexed by Spotlight reads as missing. Look at anything it prints before removing it. The same leftovers are the subject of what uninstalling leaves behind.