Symptoms
- Disk cleanup finishes but available space barely changes
- 'Low disk space' warning persists after cleanup
- Storage breakdown shows a large 'Other' or 'System' category
- Cleanup tool hangs or crashes partway through
Likely causes
- CommonLarge files outside the cleanup tool's scopeDownloads, videos, or app data folders aren't touched by basic cleanup tools.
- CommonOld system restore points or update backupsWindows keeps backup data from previous updates that can take up many gigabytes.
- CommonHidden or cached files from specific appsApps like browsers, photo editors, and cloud sync tools cache large amounts of data.
- PossibleDuplicate or forgotten large filesOld backups, ISOs, or video files often go unnoticed.
What to do
- Use a storage breakdown tool (built into Windows Settings > System > Storage, or 'About This Mac' on Mac) to see what's actually using space.
- Empty the Recycle Bin or Trash, which doesn't free space until emptied.
- Clear browser and app caches from their individual settings.
- Uninstall unused large applications.
- On Windows, use Disk Cleanup's 'Clean up system files' option to remove old update backups.
- Move large files like videos and photos to external storage or cloud storage.
- Restart the computer after cleanup to let system caches clear fully.
When to call a pro
If storage fills up repeatedly despite regular cleanup, consider a larger internal or external drive.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.