What could be slowly taking up space on my PC?

Run a disk space analyzer and sort the folders by size. WizTree, WinDirStat, and TreeSize Free can all help you work down from the drive into the largest folders. Run the scan again after some space has disappeared and compare the folder sizes. The biggest folder isn't necessarily the one that's growing, so the comparison matters.

If you see a system folder or a file you don't recognize, check what it belongs to before deleting anything. Some system files won't be fully visible without administrator permissions.

Try searching in File Explorer for files created or modified recently. Check once, leave the PC alone for an hour or two, then check again. Repeat while using it normally. That might give you a clue whether a background process or something you open is writing files.

Temporary files, logs, browser caches, and system snapshots can all use space. Games may also create more data as you play. Check Windows storage settings to see which categories are large, then investigate the ones that keep growing.

Storage Sense can clean up some temporary files automatically, but check its settings first. It can also be configured to empty the recycle bin or delete older files from Downloads.

Malware is one possibility, but a dropping space figure alone doesn't establish that. If you find an unfamiliar process or suspicious files growing rapidly, run a security scan as well as checking what created them.