Hibernation files are used for hybrid sleep, fast startup, and standard hibernation (described earlier). There are two types, differentiated by size, a full and reduced size hibernation file. Only fast startup can use a reduced hibernation file.
|Hibernation file type
||hiberfil.sys default size
||40% of physical memory
||hibernate, hybrid sleep, fast startup
||20% of physical memory
is a power-saving S4 state designed primarily for laptops, and might not be available for all PCs (PCs with InstantGo don't have the hibernate option). While sleep puts your work and settings in memory and draws a small amount of power, hibernation puts your full current state (ex: open documents and programs) on your hard disk to the hiberfile (C:\hiberfil.sys), and then turns off your computer. Hibernate uses less power than sleep and when you start up the PC again, you’re back to where you left off (though not as fast as sleep). Use hibernation when you know that you won't use your laptop or tablet for an extended period and won't have an opportunity to charge the battery during that time.
is a special state that's a combination of the S1-S3 sleep and S4 hibernation states, it's when a system uses a hibernation file with S1-S3. It's only available on some systems. When enabled, the system writes a hibernation file but enters a higher-powered sleep state. If power is lost while the system is sleeping, the system wakes from hibernation, which takes longer but restores the user's system state.
(aka: hiberboot, hybrid boot, or hybrid shutdown) is turned on by default in Windows and is a setting that helps your PC start up faster after shutdown. Even faster than hibernate. Windows does this by saving an image of the Windows kernel and loaded drivers to the hiberfile (C:\hiberfil.sys) upon shutdown so when you start your PC again, Windows simply loads the hiberfile (C:\hiberfil.sys) into memory to resume your PC instead of restarting it.
Fast startup requires that hibernate be enabled. If you only want to use fast startup and don't plan on using hibernate, then you can specify the hiberfile type as reduced
to significantly reduce the size of the hiberfile (C:\hiberfil.sys) to about half of its full size.
This tutorial will show you how to specify the desired hiberfile type
to be reduced or full in Windows 10