Your PC May Not Have Fully Shut Down Since 2012 Due to Windows Fast Startup

There is a hidden fact in the Windows operating system that many users are unaware of. If you have been using any version from Windows 8 to 11 on your computer, chances are your PC has not fully shut down since 2012.

While cleaning their NVMe SSDs using software like WizTree, many users often find a massive file named hiberfil.sys—taking up to 12.5 GB—on their C: drive. This file only appears when the Hibernation option is enabled in the system. The Fast Startup feature, included in Windows since 2012, uses this exact file every time you turn off your computer. Although it helps the computer boot up faster compared to a normal boot process, it carries some serious technical drawbacks that users should understand.

What is Windows Fast Startup and How Does It Work?

The reality is that Windows does not shut down your PC the way you think it does. If you have an older PC that upgraded from Windows 8, you likely turn off your computer by clicking the Shut Down button on the taskbar. However, doing so never actually shuts down your computer completely.

When this feature is active, Windows closes your apps and logs out the user session, but it does not fully shut down the core part of the system. In this process, the main Windows Kernel, loaded device drivers, and the operating system layer that manages hardware all remain in a loaded state. Instead of clearing everything and shutting down, Windows takes a snapshot of that state and saves (hibernates) it to the hiberfil.sys file on your boot drive.

The primary goal is to shave off a few seconds from the boot time. When you turn the computer back on, instead of starting all drivers and sub-systems from scratch, Windows directly loads that saved snapshot into system memory. This can be considered a middle ground between a full shutdown and hibernation—a process Microsoft originally named "Hybrid Shutdown."

Invisible Problems of Fast Startup

While this default feature from Microsoft sounds beneficial, it can cause many unexpected issues on desktops. The root of most technical glitches seen since Windows 8 traces back to this feature. Because the PC never fully shuts down and the Kernel State is never reset, it frequently causes complex issues over time.

Among the problems reported by users and tech analysts, conflicts with Windows Updates are the most prominent. According to a 2017 report published by Microsoft, certain updates require a full system shutdown to install completely. Because Fast Startup hibernates the kernel instead of closing it, those updates do not take full effect until you choose the Restart option. For this reason, Microsoft urged Windows 10 users to select Restart instead of Shut Down to complete updates.

This problem was not limited to Windows 10. A aspect of it was not resolved until the KB5067036 patch in October 2025. According to Windows forums, choosing "Update and Shut Down" resulted in an issue where the computer kicked the user back to the lock screen instead of turning off—with Fast Startup being identified as the main technical cause.

Over the past decade, this feature has caused driver and firmware updates to fail, peripheral devices like keyboards and mice to stop working, and minor technical glitches to surface due to improperly applied updates. Performing a Restart forces a Cold Boot, which completely resets the system. That is why many issues seen in Windows 10 and 11 are resolved simply by restarting.

Should You Keep This Feature Enabled?

Today, many tech analysts argue that Fast Startup is no longer necessary. Because modern SSDs are naturally fast, this feature makes very little difference to the overall user experience. Disabling it requires tweaking just a few simple settings.

However, it remains true that it saves a few seconds of boot time. On a desktop PC running a single operating system, it doesn't cause major harm. But for laptop users, this feature can still be quite handy. Since laptops are opened and closed frequently, saving those few seconds is noticeable. Many laptop users hesitate to use Sleep mode out of fear of draining the battery, making Fast Startup a practical alternative for them.

Real User Experiences

Users have faced odd issues due to this feature. According to a user named Rick-H, his laptop would boot up on its own, log into the admin account, and leave the screen unlocked. His system stabilized only after he turned off Fast Startup.

Similarly, another user named Renos shut down his computer and removed an external drive. After transferring files to it on another PC and reconnecting it to his computer, Windows failed to show the new files. The files occupied storage, yet were nowhere to be seen. Disabling this feature resolved his issue.

Fast Startup also became a headache for GPU miners, as it retained old GPU firmware; even after updating to new firmware, it would continue running the old version.

Fast Startup was a suitable feature for the era of slow storage (HDDs). With advancements in modern technology, looking at the update glitches and storage consumption it causes, whether you need this feature depends on your specific needs. It may still be helpful for those using older PCs or legacy drives, but for those seeking system stability, turning it off seems to be the best choice.