Freeing up disk space,without losing anything
“Your startup disk is almost full.” The message keeps coming back, you close the window, and one day the Mac refuses to install an update or import photos. There is an order to follow when making room.
What is actually going on
A full disk does not merely slow the machine: it stops it working. macOS needs free space for updates, temporary files and indexing your documents. Below ten gigabytes or so, everything turns sluggish.
The bulk rarely sits where you think. It is usually old iPhone backups, duplicate photo libraries left over from a migration, files under the opaque “System Data” heading — and sometimes a trash never emptied in years.
What we do
- Take stock of what fills the diskFolder by folder, with a proper measuring tool. The starting picture prevents regrets.
- Take things out before deleting themPhotos, videos and old documents go to an external drive or to iCloud first. Only then do we free space.
- Deal with “System Data”That opaque category is mostly backup snapshots and caches. It can be reduced, cleanly.
- Set up storage optimisationSo the Mac keeps what you use locally and leaves the rest in iCloud, without you having to think about it.
Before we arrive
What helps
- Have an external drive ready if you have a lot of photos or video to move out.
- Empty the trash after our visit: while it is full, the space is not given back.
What is better avoided
- Deleting system folders to gain a few gigabytes.
- Switching off iCloud “to get space back” — the opposite happens.
Your questions
How much free space should I keep?
A good rule: at least 15% of the disk, and never less than 20 GB. Below that, the trouble starts.
Do my photos really leave the Mac if I turn on iCloud?
The originals go up to iCloud and the Mac keeps lighter versions. You see everything and use less space — provided the storage plan is big enough.
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