Freeing up space · Free Up Space wizard and button
What is the "Nothing has happened yet" review step?
Short answer: It's the review shown after you choose Free up space: each ticked option opened one level with real measured sizes, plus how much you'd gain. Nothing is touched until you confirm.
It's the review you always get after choosing Free up space — pressing the button doesn't start anything. Every option you ticked is opened up one level, with the real measured size of what's inside, so you can see exactly what you're agreeing to before a file is touched.
It also tells you what you'll gain in plain terms: roughly how much this frees, and what your free space would be afterwards compared with now. Sizes are measured as you tick, so you aren't kept waiting.
Only when you confirm does the work begin, and the same sheet then becomes the progress view. See why a size may still be counting.