hiberfil.sys is the hibernation file at the root of your system drive, C:\hiberfil.sys. Windows uses it to save the full contents of RAM to disk when the PC hibernates, so you can power off completely and resume exactly where you left off. You can't delete it directly, but you can remove it by turning off hibernation:

powercfg /h off

Run that from an elevated Command Prompt (Run as administrator) and the file is removed, freeing several GB.

TL;DR

  • hiberfil.sys stores your RAM image so Windows can hibernate and support fast startup.
  • It's normally about 40% of installed RAM (around 6 GB on a 16 GB PC).
  • Remove it with powercfg /h off; restore it later with powercfg /h on.
  • Don't delete it in File Explorer; it's a protected system file and Windows will block or recreate it.
  • Disabling hibernation also disables fast startup, so cold boots may be slightly slower.

Why is hiberfil.sys so large?

Hibernation works by writing everything currently in RAM to disk, then cutting power. To do that, the file must be big enough to hold a meaningful share of your memory. Windows sizes it at roughly 40% of installed RAM by default, so more RAM means a bigger hiberfil.sys. A 32 GB machine can easily carry a 12 GB+ file you never see, because it's hidden and protected.

The file also backs fast startup, the feature that makes Windows boot quickly by hibernating the kernel session rather than shutting down fully. So even if you never click "Hibernate," the file is likely still there.

How do I delete hiberfil.sys safely?

The supported way is to disable hibernation, which removes the file automatically:

powercfg /h off

To re-enable hibernation (and recreate the file) later:

powercfg /h on

If you want to keep hibernate but use less disk, shrink the file instead of deleting it:

powercfg /h /size 50

That sets the hibernation file to 50% of its default size. Do not attempt to delete C:\hiberfil.sys in File Explorer; it's protected and the deletion will fail or the file will reappear.

What Windows does natively, and where it stops

Windows creates and maintains hiberfil.sys whenever hibernate or fast startup is enabled, sizing it automatically and keeping it ready. On laptops, hibernation is often on by default to protect work when the battery dies.

Where it stops: Windows never removes this file to save space, even when your drive is nearly full, and neither Storage Sense nor Disk Cleanup will touch it. If you don't use hibernate, that space stays reserved indefinitely until you run powercfg /h off yourself.

What this cannot do, and when not to delete it

Removing hiberfil.sys only helps once; it frees its own size and nothing more. It won't fix general slowness or clear app caches, so treat it as a one-time space win, not a maintenance routine.

Don't disable hibernation if you actually use it. Laptop users who rely on hibernate to preserve a session through a dead battery should keep it; turning it off means an unsaved session is lost when power runs out. You'll also disable fast startup, so some PCs boot a few seconds slower afterward. And never force-delete the file manually; always use powercfg, which lets Windows tear it down cleanly and recreate it on demand.

For bigger reclaimable space, see how to find the largest files on Windows 11 without third-party apps. If you're weighing NTFS compression as an alternative, check is it safe to compress the C: drive to save space first.

FAQ

Will deleting hiberfil.sys break Windows?

No, as long as you remove it properly with powercfg /h off. That cleanly disables hibernation and deletes the file. You only risk problems if you try to force-delete the protected file by other means.

How much space will I get back?

About the size of the file, which is roughly 40% of your installed RAM. On 16 GB of RAM that's around 6 GB; on 32 GB it can be 12 GB or more.

Can I turn hibernation back on later?

Yes. Run powercfg /h on from an elevated Command Prompt and Windows recreates hiberfil.sys and restores both hibernate and fast startup.

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