My disk is almost full but I don't think so

[TheAnh]

(Sorry if my English is not good)
So, I've just bought a new laptop - Dell XPS 13/Windows 10/256GB SSD. I downloaded some games, and they do take a lot of disk space (C:), especially Fortnite (about 21GB). Since then, I haven't downloaded anything else, just play games and surf the web. I remember that a few days ago, the disk's free space is more than 20GB, and today, it decreased to 18,2GB. Again, I haven't downloaded anything else, it just decreased. I don't know if it is the cache, or history, or anything has taken more disk space. Today I opened the disk's properties, and while it said I used 69,2GB, all the files in the disk takes only 53,6GB. Where has the other 15,6GB gone? Is there anything I can do to restore all the lost disk space?

[skypuppy]

Could be "pagefile.sys" if Win10 still calls their "virtual memory" (swap space) by that filename.  If tasks exceed physical RAM, the OS starts swapping tasks, data, and etc. out to disk and back.

If it bothers you a great deal, you can set the "virtual memory" to a fixed size rather than allow Windows to use as much as is needed, but you run the risk of it crashing BSOD if memory requirements get too high, and it sounds like your games would easily create that problem.

[Salmon Trout]

Also hiberfil.sys if hibernation is enabled.

[Mark.]

personally, I'd go into Control Panel, System,Advanced system settings, Advanced tab, Settings, Advanced tab, Change, untick Automatically manage, and select Custom size and set min to 512 and max to 8192, and click Set and OK.
and while in Control Panel, System properties window, click System Protection tab, Configure and set Max Usage to 1% for Restore Points, and delete the ones already stockpiled.
you could then start an elevated command prompt and type powercfg -h off to turn off hibernation if you don't use it.

that should reclaim a few gigs.
get WizTree from https://antibody-software.com/web/software/software/wiztree-finds-the-files-and-folders-using-the-most-disk-space-on-your-hard-drive/ and it'll find where all your space has gone.

and do a cleanup using the inbuilt cleaner by starting an elevated command prompt and typing the command cleanmgr c: /sageset:1tick all the boxes and click OK.then type cleanmgr /sagerun:1
if you are still short on space, it's time to be ruthless and remove stuff off the SSD and onto an external drive or into the cloud.

[techbeard]

It could also be windows updates and feature updates causing the issue, I've see this on machines with SSD's and tablets.  Run Disk Cleanup and then click on the button that says cleanup system files, there you can removed files that windows updates left behind and old windows files from an upgrade.

[brav3]

Happened to me with a 250 ssd to 20gb, try to see if there's an "Windows.old" in you drive C: if there's you can search how to remove, it will give you a 10-20gb space if I remember it correctly Also windows update was sometimes the culprit in my experience. Hope it helps, good luck