Freeing up space · Free Up Space wizard and button
What does the cache cleanup step of Free Up Space look at?
Short answer: Step 1 lists well-known cache locations — developer, browser and container build caches — with sizes. Untick anything you want to keep, then confirm; the deletion is staged so nothing is left half-deleted.
Step 1 scans the well-known cache locations on your Mac and shows them as a checklist with sizes: developer build and package caches, browser disk caches, and container build caches. You untick anything you'd rather keep, then confirm.
The deletion is staged, so if something interrupts it — a crash or a power cut — a folder isn't left half-deleted. Caches are data apps rebuild for themselves, so the cost of clearing them is a slightly slower first launch or build, not lost work.
The exact list is in Which developer caches does Free Up Space clear? and Does it clear browser caches?