Hiberfil.sys in Windows 8 and Why You Should Never Disable Hibernation To Delete It

We explained it before what is hiberfil.sys on Windows 7 computers and how to permanently delete it to free up some hard drive spaces. It’s no longer the case on Windows 8. Why? Because it’s been assigned a special task for a feature that everyone would love and appreciate.

Windows 8 fast boot

Windows 8 introduces a fast, new startup capability that allows Windows 8 to boot much faster than any previous Windows system, including Windows 7. To make this happen, Microsoft optimized the way how normally a Windows machine shuts down. Instead of a full shutdown that basically closes the kernel session, Windows 8 hibernates it to save the kernel session, which is much smaller than a full hibernation, to the disk, more specifically, to the hiberfil.sys file. It makes a faster boot time because resuming the hibernated system session is comparatively less work than doing a full system initialization.

Therefore, unless you deadly need that a few gig space back, you should never disable hibernation on Windows 8. Doing so would result in the permanent removal of the hiberfil.sys file, which would leave no place for the kernel session to be stored, meaning that the fast startup process usage of a saved kernel session would not be possible. You would find your Windows 8 startup takes longer to finish.

How big is hiberfil.sys?

Typically, the hiberfil.sys is sized by default at 75% of physical RAM you have installed on your system. And you can customize the size by running

powercfg /h /size <percentage_size (0 – 100)>

in Command Prompt as Administrator window.

Powercfg size

How to check if hibernation is on

If the file hiberfil.sys listed from the following command, the hibernation is turned on.

dir c:\ /ah

check hibernation

To turn off Hibernation

Run the following command in Command Prompt as Administrator:

powercfg /h off

The hiberfil.sys will be removed immediately after it’s run.

To turn back on hibernation

Run the following command in Command Prompt as Administrator:

powercfg /h on

The result is immediate.

Kent Chen

Microsoft MVP, IT Professional, Developer, Geek, and the co-founder of Next of Windows.

Last updated: 10/28/2014

Posted in: Windows 8
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Frew Cen
Guest

I would note that hiberfil.sys can cause (and causes) problems when running two operating systems on one machine. For example lastest Ubuntu LTS refuses to show login screen until the hiberfil.sys is removed (so you need to log out and delete it somehow), and Linux Mint fires error dialog every startup.

A Software Developer.
Guest
A Software Developer.
32GB of RAM here, but the boot disk is a 2x 128GB SSD RAID-0 array. That 32GB file is expensive, and I can quantify that financially. I tried setting it to something sane, like 13% (which would be 4GB), and it will not reduce itself to below 16GB. I feel I’m somewhat justified in disabling this “feature”. This is a development machine and we need all the space on that SSD that we can get. Powercfg /h off is what we used on 7. I’d be fine if they’d just give the the ability to move it to the 4tb… Read more »
Bill
Guest

This is stupid, it eats up lots of space from a fresh installed win8x64 on ssd + windows 8 “fast startup” corrupts other filesystems (EXTFS, HFS ETC)

Bruno
Guest

Saved me 27gb of SSD… that’s one huge file…

Daniel Earls
Guest

Powercfg.exe /hibernate off In command promt( admin) in windows 8

s1aver
Guest

Isn’t it only for brand new computers that have a UEFI bios that can utilizes the new hybrid kernel for fast boot up. For any other computer wouldn’t the hiberfil.sys file just wastes space.

Kent Chen
Guest

UEFI is mostly for improving security and the ability to boot from an over-2TB HD, not much different for speeding up the boot process.

In general, hiberfil.sys helps more in terms of faster boot-up. You should always enable it unless you are running off on a SSD.

s1aver
Guest

Thanks for the correction. I’ll go renable hibernate on my PC.

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