If you do check your computer for large files that use lots of disk space chance is that you will come upon a file called hiberfil.sys on your main Windows drive eventually.
The file is hidden by default, but you can change that in the folder options. Some third-party programs display it directly, but if you browse Windows Explorer or another file manager, you may not spot it until you make the change and display operating system files by default.
The hiberfil.sys file has a size of several Gigabytes on modern computer systems. On a test system with 8GB of memory running Windows 8 it used about 6.6 Gigabytes of hard drive space.
Depending on how much free space that drive has available, it may be a lot. This has become more of an issue lately again with the rise of Solid State Drives of which many don't offer large storage capacities yet.
The file itself is used to hibernate the system. Whenever you use Hibernate on your computer, Windows takes a snapshot of the current session and saves it to disk. This includes the running programs, open documents, windows that are open and everything else of importance.
The main idea behind the feature is to speed up the loading of the session on next start. It was originally designed for mobile PCs such as laptops, but can also be used on desktop PCs.
The file may be as large as the total amount of RAM installed on the computer, but is usually less on modern systems thanks to compression used by those newer versions of Windows.
The file is large and while it has its uses especially on mobile devices, you may want to consider disabling the feature, especially if you are using a desktop PC and don't make use of it regularly or at all.
The best way to delete hiberfil.sys would be if you did not use Hibernation at all. The feature is enabled in most notebooks sold and can be easily deactivated. Go to Control Panel, choose Power Options, click on Hibernate and uncheck Enable hibernation.
If you disable Hibernate, the functionality is no longer available. You can switch to any other power state though, which means that shutdown and sleep mode are working just like before.
The only other effect is that you free up several Gigabytes of storage space on your hard drive as hiberfil.sys gets deleted in the process.
When you disable Hibernate, the hiberfil.sys file will be automatically deleted. To do this on newer versions of Windows, do the following:
This turns off Hibernate on the system and will delete the large hiberfil,sys file on the PC as well freeing up space in the process.
If you need Hibernation simply run the same steps outlined above but use powercfg -h on instead as the command.
You will notice that Hibernate is no longer an option when you select shutdown on your system, but that should not be a problem if you never used it anyway or can live without it.
Update: With memory in modern computer systems increasing, so does the size of the Hibernation file in Windows. To avoid 8, 12 or even 16 Gigabyte Hibernation files Microsoft has introduced a compression feature into Windows 7 that is trying to keep the size of the file at a much lower level. Keep in mind though that Vista and XP do not support that new feature, and that you might see a very large Hibernation file as a consequence.
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Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.