Mac storage basics · Apps and macOS itself
Will reinstalling macOS free up storage space?
Short answer: Not much — a reinstall replaces macOS but keeps your apps, files, caches and backups. Only erasing and starting fresh clears everything, which is rarely necessary.
Not much. Reinstalling macOS from Recovery replaces the system but keeps your apps, files and settings — and the data that fills disks (caches, libraries, backups) stays where it is.
A real clean start means erasing the Mac and setting it up again, then restoring only what you need. That's a big step; targeted clean-up of System Data, apps and big files usually gets the space back with far less effort.