As explained in this XDA article, when you click Shut Down on your Windows 11 PC, your PC doesn't really shut down, at least, not in the way you'd expect it to. What the system does is basically log you out, take a snapshot of the kernel (which manages your hardware and anything running on top) along with your loaded drivers, compresses that snapshot, and writes it to a hidden file on your main boot drive (usually C: for most users) called hiberfil.sys. The next time you power on, Windows reads that file back into memory. This saves quite a bit of time, and that's why it's aptly named Fast Startup. It's a form of hibernation running behind the scenes on every shutdown, whether you asked for it or not. I came across this accidentally while going through a disk-space audit on my machine, wondering why my NVMe, which should have plenty of headroom, kept feeling tighter than it should, while installing some local AI models. With a quick scan via WizTree (a utility that maps what's exactly eating your storage), I found a 12.5GB hiberfil.sys file in sight, sitting as one of the largest single files on my entire drive. There is an option to keep hibernation intact and switch off Fast Startup. If you open the Control Panel, go into Power Options, and then select, "Choose what the power buttons do", you might notice the checkbox is greyed out. You'd have to click, "Change settings that are currently unavailable" above it, and then untick "Turn on fast startup", and simply save. Your shutdowns from this point on will actually shut down your PC, although the hiberfil.sys file will stay put. The other option will help you reclaim the disk space for you. You can right-click Start, open Terminal as an Administrator, and type powercfg /h off, and then hit Enter. This will delete the hiberfil.sys file and hands you back the space. In my case, it was about 12.5GB. It's worth noting that this is a fully supported Microsoft command and not a hack. It's also reversible with the same command, you'd just have to substitute "off" with "on." Laptop owners do have a little something to think about when following these steps, though. Hibernation saves your session if the battery gives out, and using powercfg /h off gets rid of that safety net if you were relying on it. If that describes you, the option of the two is the safer pick, since it saves your SSD from the wrath of Fast Startup's daily writes while leaving Hibernate available when you choose to trigger it manually.
[EOP]
