Running out of space — what's safe to delete
A full drive doesn't just stop you saving things — it slows the whole machine down and can block Windows updates, which is a security problem as well as an annoyance.
The good news is that the space is usually taken by a few predictable things, and you don't need any special software to reclaim it.
Find out where it's actually gone
Guessing wastes an evening. On Windows, Settings then System then Storage breaks it down by category. On a Mac, the Apple menu, System Settings, General, then Storage.
For a clearer picture, the free tool WizTree (Windows) or the built-in storage view (Mac) shows which folders are biggest, which usually answers the question in about ten seconds.
Safe to clear
These are the usual culprits, and none of them will break anything.
- Temporary files — use Windows' own Disk Cleanup or Storage Sense rather than a third-party cleaner
- The Recycle Bin, once you've glanced through it
- Your Downloads folder — almost always gigabytes of installers you'll never need again
- Old Windows update files and a previous Windows installation (Windows.old), if you're happy with the current version
- Programs you don't use, uninstalled properly through Settings
- Video files: old recordings, downloaded films and game captures dwarf everything else
Leave these alone
Deleting the wrong thing here causes far more trouble than a full drive.
- Anything in Windows, Program Files or System32
- Files you don't recognise in the root of the C: drive
- The hibernation or page file, unless you know exactly why you're changing it
- A recovery partition — it's what restores the machine if Windows won't start
- Anything a search result tells you to delete from the registry
The cloud trick most people miss
If you use OneDrive, iCloud or Dropbox, switch on the option that keeps files online until you open them — Files On-Demand on OneDrive, Optimise Storage on a Mac. Everything stays visible and available, but only what you actually use takes space locally.
On a laptop with a small drive this alone often solves the problem, and it's reversible.
When it's a hardware answer
If you're clearing space every few weeks, the drive is simply too small. A larger SSD is inexpensive, and on a desktop or an older laptop it's a straightforward upgrade that usually makes the machine faster at the same time.