Finding and Managing Windows’ Hibernate File (hiberfil.sys)

Ever noticed a mysterious file called hiberfil.sys hogging several gigabytes on your C: drive? That’s Windows’ way of remembering the exact state of your computer when you hit Hibernate. It’s not a virus, but it can be a bit of a space‑eater, especially on smaller SSDs.

First things first: the file lives at the root of the system drive, usually C:\hiberfil.sys. You won’t see it in File Explorer by default because it’s a protected system file. To catch a glimpse, you have to turn on the “show hidden files and protected operating system files” option, or just use the command line.

Opening a Command Prompt with administrator rights and typing dir C:\hiberfil.sys /a will list the file, confirming its size. The size is roughly the amount of RAM installed—so a machine with 16 GB of memory will reserve about 16 GB for hibernation.

Why does Windows need that much space? When you hibernate, the entire contents of RAM are written to hiberfil.sys. On the next power‑on, Windows reads that file back into memory, restoring every open document, program, and setting exactly where you left it. It’s a handy feature for laptops on the go, but if you never use it, you can safely shrink or disable it.

To disable hibernation (and delete the file) open an elevated Command Prompt and run:

powercfg -h off

This command turns the feature off and removes hiberfil.sys automatically, freeing up the disk space. If you later decide you miss the convenience, simply run powercfg -h on and Windows will recreate the file at the appropriate size.

Sometimes you might want to keep hibernation but reduce its footprint—perhaps you have a 32 GB SSD and 16 GB of RAM. In that case, Windows 10 and 11 let you set a “hibernation file size” percentage. Run:

powercfg -h -size percentage

Replace percentage with a number between 40 and 100. For example, powercfg -h -size 50 will make the file roughly half the size of your RAM. This trade‑off may slightly affect resume speed, but it can reclaim valuable storage.

Remember, any change to hibernation requires a reboot for the system to re‑evaluate the new settings. After restarting, you can verify the new file size with the same dir command as before.

In short, hiberfil.sys lives at the root of your Windows drive, mirrors your RAM size, and can be toggled or resized with a simple powercfg command. Knowing where it is and how to control it lets you keep your PC running smoothly without mysterious space‑hungry surprises.