Freeing up space · Local snapshots and held space
How do I free a specific amount of space from snapshots before a macOS update?
Short answer: In Local Snapshots, type the amount you need under Custom reclaim and click Reclaim now. It's useful when, say, a macOS update needs a set amount of free space.
Use Custom reclaim at the bottom of the Local Snapshots window. Type the amount you need and click Reclaim now; Storage Studio clears snapshots to free that much, following the same safety rules as everywhere else in the window.
It's handy when a specific task needs a set amount of room — for example a macOS update asking for a certain amount of free space. The result is shown in the outcome banner, which you can dismiss.
If snapshots aren't holding enough, look at What's Using Space or Emergency Space for the rest.