When you click “Shut Down,” your screen goes black, and you assume your PC has actually “shut down” in the original sense of the phrase. However, on most modern Windows PCs, that isn’t the case.
Since Windows 8, Microsoft has used a feature called Fast Startup that saves some parts of a session to the disk instead of closing it, then reloads that information the next time you boot up.
It made sense originally; today it is mostly just a source of problems.
What actually happens when you click shut down now?
Fast Startup stops you from truly shutting down
When your PC actually shuts down—either via a button press or a power loss—every process closes, drivers are all unloaded, and your RAM is cleared. Your PC is close to a blank slate.
Fast Startup changes that. Rather than tossing out the state of your operating system (your kernel state specifically), it saves it to your storage drive in the hiberfil.sys file. When you turn your PC back on, your system loads from that saved state rather than loading fresh from the operating system files.
Fast Startup doesn’t make sense anymore
NVMe drives and modern chipsets make the time savings negligible
Back when the feature was introduced, most PCs relied on mechanical hard drives and CPUs were much slower. Booting could easily take a few minutes. By skipping the kernel initialization, Fast Startup actually did save a significant amount of time.
The problem is that modern PCs aren’t booting off a spinning platter. A quick test on my own PC showed it booted in less than 15 seconds. Modern firmware initializes faster (usually), and CPUs handle the boot process far more efficiently than they did a decade ago. The real time savings are small, if they exist at all.
You are essentially carrying the risks of a stale kernel state for a boot-time improvement that you probably can’t even perceive. It is solving a problem that most current hardware simply doesn’t have anymore.
The Fast Startup can cause a million different glitches
Weird driver and hardware bugs
Because the kernel session is restored from the disk, your drivers never fully reinitialize after a “shut down.” This leads to weird bugs where Bluetooth devices suddenly won’t pair, USB devices aren’t recognized, or your audio randomly isn’t working. When you read the advice “restart your computer to fix the issue,” it’s because a restart is the only way to guarantee that everything actually starts from a clean slate. Turning the PC off and back on doesn’t work like you’d expect, which is an extremely common problem.
Dual-boot setups and shared drives are the hardest hit
If you use a dual-boot setup, Fast Startup is a liability. It locks the Windows NTFS partition. If you try to mount that partition from Linux—like you might to move files between your Windows install and your Linux install—you’ll likely encounter write errors. If you forcibly override it, you could even corrupt some data.
Similarly, if you remove an external drive during a shutdown with Fast Startup enabled, it might not unmount correctly, which could pose a risk to your data. Thankfully, that risk is fairly small.
Windows Update failures and patches that never fully apply
Some Windows updates require a clean kernel boot to finish installing. Because Fast Startup skips that step, you can end up in update loops, failed patches, or the undoing changes screen. Even Microsoft’s own troubleshooting documentation occasionally tells you to disable Fast Startup to fix these issues.
How to actually Shut Down your PC
One command disables Fast Startup permanently
If you want your PC to actually shut down, you can do it with one command. Run PowerShell as administrator and run the following command:
powercfg /h off
This disables hibernation entirely, which removes Fast Startup as a side effect and frees up any disk space used by the hiberfil.sys file. Every time you click shut down after that, your PC will completely shut down, just like restarting your PC or disconnecting the power.
Alternatively, clicking the Restart button will always work as you’d expect. If you don’t care to disable Fast Startup, make sure to actually click Restart instead of clicking Shut Down.
Keep Fast Startup if you’re using old hardware with a slow boot drive
If you are still running a spinning hard drive and the time savings you get are substantial, Fast Startup still serves a purpose. For everyone else—especially dual booters, people troubleshooting hardware glitches, or anyone who just expects “Shut Down” to actually mean shut down—you should turn it off.