C:\hiberfil.sys is a snapshot of your RAM that Windows writes to disk for hibernation and Fast Startup. It scales with installed memory — on a 32 GB laptop, expect ~13–24 GB of hiberfil.

Short answer: open an admin Command Prompt and run powercfg -h off. Reboot — hiberfil.sys is gone and you keep that space back.

Why hiberfil.sys is so large

Windows sizes it at roughly 40–75% of installed RAM. The file does two things:

  • Hibernate — copies RAM to disk so you can fully power off and resume exactly where you left off
  • Fast Startup — on shutdown, Windows hibernates the kernel session (not your apps), so the next boot is faster

If you always use Sleep or Shut down (not Hibernate) and do not care about Fast Startup shaving a few seconds off boot, disabling hibernation is pure win.

Turning it off

  1. press Start, type cmd
  2. right-click Command Prompt and choose Run as administrator
  3. run powercfg -h off
  4. reboot

After reboot hiberfil.sys is deleted and the Hibernate option is removed from the power menu. Sleep and Shut down both continue to work normally.

How to turn it back on

  1. open Command Prompt as administrator
  2. run powercfg -h on
  3. (optional) cap the file size: powercfg -h -size 50 sets hiberfil to 50% of RAM (range 40–100)

Trade-offs to know

  • you lose the Hibernate power option
  • Fast Startup stops working — next cold boot is a few seconds slower
  • on desktops and plugged-in workstations these trade-offs are invisible; on laptops you rarely unplug overnight, same

Better next routes

For more "System & reserved" shrinking, continue with Why Does "System & Reserved" Take So Much Space on Windows?.

For the broader Windows 11 cleanup, read How to Free Up Space on C Drive Windows 11 Natively.