Written by
Wilsey YoungSummary: This article revolves around the hiberfil.sys file in Windows operating systems, exploring what it is, how it works, and whether we can remove it to free up disk space. -From m3datarecovery.com
hiberfil.sys is a system-protected file in Windows, and it can take a significant amount of disk space on your PC. Many Windows users wonder what it does and if it can be safely deleted for disk cleanup. This post covers almost everything you want to know about hiberfil.sys file on Windows.
What is hiberfil.sys file and how does it work?
The hiberfil.sys, also known as the hibernation file, is a system file that the hibernate mode and Fast Startup feature on Windows rely on to function. When you click the "Hibernate" button in the "Start" menu, Windows saves your session, including open apps, programs, and files, etc., to the hiberfil.sys file stored in HDD/SSD. 
When you turn your Windows PC back on, Windows reads the hiberfil.sys file and restores the previous working state to where you left off, which is much faster than manually reopening everything.
You may be interested in Hibernate Mode vs Sleep Mode on Windows: Key Differences!
hiberfil.sys is typically located in the system drive, and how much space it occupies depends on the RAM size. The hiberfil.sys file size is approximately 75% of the RAM installed on your PC. For instance, if your PC has 16GB RAM, the hiberfil.sys size may reach 24GB.
As a side note, hiberfil.sys is hidden, by default, in Windows because of its significance. Here's how to check it in Windows:
- Double-click "This PC" or "My Computer" on the "Desktop" to open "File Explorer."
- Open the "System (C:)" drive, aka Local Disk C: or System Drive.
- Click the "View" tab and tap on "Options."
- Under the "View" tab, select "Show hidden files, folders, and drives", and uncheck "Hide protected operating system files (Recommended)."
- Click "Apply" and "OK" to save changes.
- Check where hiberfil.sys is.
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Can we delete hiberfil.sys?
Technically, yes, but if you delete hiberfil.sys directly from the File Explorer, Windows will recreate it automatically as the hibernation feature is still enabled. Therefore, you can disable the hibernation mode to let Windows delete the hiberfil.sys file automatically, and more free disk space will be gained.
To disable the hibernate mode, follow the steps below:
- Open "Control Panel" by searching for it in the Windows search box.
- Switch to "Large icons" and choose "Power Options" from the menu.
- Tap on "Choose what the power buttons do" from the left side panel.
- Click "Change settings that are currently unavailable."
- Uncheck "Hibernate" and "Turn on fast startup (recommended)."
- Tap on "Save changes."
Alternatively, you can disable the hibernate mode via the Command Prompt:
- Press the "Windows+S" keys to open the Windows search box.
- Type "cmd" and select "Run as administrator."
- Input "powercfg /hibernate off" into the command window and hit the "Enter" key on your keyboard.
If you want to re-enable it, run Command Prompt and execute the command below:
powercfg /hibernate on
This re-enables hibernate and Fast Startup and recreates the hiberfil.sys file.
How to reduce hiberfil.sys size?
By default, the hiberfil.sys size is equivalent to about 75% of the installed RAM on your PC. Windows also allows you to reduce the space allocated to hiberfil.sys, which is helpful, especially when you want to reduce the hiberfil.sys size, but leave the hibernate mode on.
The following command sets hibernation to a smaller size, enough for Fast Startup to work, but not full hibernation.
- Run Command Prompt as an administrator.
- Input "powercfg /h /type reduced" and hit the “Enter” key.
If you want to set hiberfil.sys file to an exact percentage of RAM used, input and execute "powercfg /h /size percent". A value no less than 50 is recommended, for example:
powercfg /h /size 50
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FAQs about hiberfil.sys
A
It’s a hidden system file located in the system drive and used by Windows to save the current session (e.g., apps, programs, and files) when your PC enters hibernation or uses Fast Startup.
A
Technically yes. However, if you directly delete the hiberfil.sys file from File Explorer, Windows recreates it automatically as the hibernate mode is still on. Luckily, you can remove hiberfil.sys by disabling the hibernate mode. To do so, execute powercfg /hibernate off in an elevated Command Prompt.
A
Windows automatically recreates a hiberfil.sys file as long as you re-enable the hibernate mode by running the command: powercfg /hibernate on