Hibernation in Windows

Hibernation: The Ultimate Session Saver

Hibernation in Windows is a power-saving state where the system saves the entire contents of memory (RAM) to a file on the disk and then powers off completely. When the device is turned back on, Windows restores everything to the exact state it was in before shutdown (open apps, documents, processes, everything) without reloading the operating system from scratch. Basically, hibernation freezes your current session, writes it to disk, and resumes later like nothing happened.

Action                                       Command                          Purpose

Check power states:                  powercfg /a                        Verify hibernate & sleep availability.

Enable hibernation:                   powercfg /h on                  Create a hibernation file & enable feature.
Disable hibernation:                  powercfg /h off                  Remove hibernation file & disable feature.
Set max size:                             powercfg /h /type full       Max RAM sleep support.
Set reduced size:                       powercfg /h /type reduced   Minimal file for Fast Startup only.

Set manual size:                        powercfg /h /size 40          40% of the total RAM in this example.
View hiberfile size:                   dir /a c:\hiberfil.sys          Confirm disk allocation & status.

 How does hiberfil.sys work in Windows??

When you put your PC into hibernation, Windows doesn’t shut down completely; it saves your entire session (open apps, files, and system state) into a hidden file called hiberfil.sys on your root of the C: drive.

 How does hibernation save the session?

Windows freezes everything in RAM. Including all open programs and system data. It compresses that data and writes it into hiberfil.sys. Once done, the PC powers off completely, but your session stays stored safely on the disk.

 How does hiberfil.sys load at boot? 

When you turn your PC back on, Windows Boot Manager sees that hiberfil.sys exists. It uses Windows Resume Loader (winresume.exe) to read and restore the data from the file back into RAM. Your desktop, apps, and files come back exactly as you left them.

Pro tip:

If you use a PC frequently throughout the day, enable hibernation for faster session recovery without draining power. Hibernation is the modern version of shutdown.

To conserve storage space, consider switching to Reduced Hibernation mode, which requires less disk space while still supporting Fast Startup.