Check the affected drive and Windows’ storage categories first. If space keeps disappearing, compare folder growth across repeated checks to find the recurring change.
Check the right drive first.
Open File Explorer → This PC and note the free space on the drive that is filling up. If you have several drives, check the drive letter carefully: a folder on another drive won’t explain a change on C:.
Write down the reading and time, then think about recent activity. A large download, a game update, or a batch of new media files gives you somewhere specific to start looking.
Two readings are more helpful than one. Compare the same drive after a normal work session to see whether its free space is still decreasing.
Review Windows’ storage breakdown.
Open Settings → System → Storage to inspect the categories using space. Review Cleanup recommendations on Windows 11 if you want Windows’ suggestions for files you could remove.
Check each selection before deleting anything. Keep downloads or personal files you still need. Microsoft explains the options in its drive-space guide.
If you use Storage Sense, review its settings separately. It can remove temporary files and older Recycle Bin items; its behavior depends on your choices. Microsoft notes that Storage Sense works on the system drive. Its Storage Sense guide explains how to review the options.
Look for what keeps coming back.
Freeing space once and watching it fill again suggests that something keeps adding data. Start with folders tied to your work: game libraries, video exports, Downloads, or a project’s generated files.
Right-click a folder in File Explorer, choose Properties, and record its Size. Check the same folder again later. Compare Size with Size; mixing it with Size on disk makes the result harder to interpret.
Look at the files behind the increase. A folder growing by several gigabytes is useful evidence, but its size alone doesn’t prove which app created the files or whether they are safe to delete.
Remember the Recycle Bin. A file can leave its original folder while continuing to use drive space until you remove it from the Bin.
Keep a history of the changes.
If manual comparisons become repetitive, let a storage tracker record them. DiskEzy for Windows checks the drives and folders you choose and keeps a daily history of observed changes.
Complete the first check, then leave DiskEzy running for later checks. Choose a day in Storage history, look for the folders that grew, and inspect their file changes. You can keep checks running in the system tray and pause them when needed.
Checks run on a schedule, so files created and removed between checks can be missed. Tracking begins with your first completed check, and recorded file-size changes may differ from the drive’s free-space reading.
See the folder-growth guide for an example of reading additions, removals, and net change together.