Fast Startup is a new feature available in Windows 8, also known as “hybrid boot” or “hybrid shutdown”. It’s purpose is to offer a faster PC start up after shutting it down. This is accomplished by saving a part of system information and device drivers to the hibernate file (hiberfil.sys). Do not mistake this with the hibernate function, which saves a lot more information in the hiberfil.sys file to restore your system to the exact state you left it in.
The stored information is then used the next time you start your computer, instead of doing a cold boot and can speed up boot time significantly. Most of that improvement comes from the reduced time needed to reinitialize drivers using the hibernate file.
In both Windows 8 and Windows 8.1, Fast Startup is turned on by default. However, here’s what you need to do if you want to disable or enable it yourself:
1. Open up the Control Panel. You can find it via Search or open it from the Win+X menu (Start button menu in Windows 8.1).
You can also get to the Control Panel by opening the Charms bar (Win+I or holding the mouse cursor in the upper-right hand corner of the screen) and select Settings – Control Panel.
2. Now you need to navigate to the Power Options panel. If your Control Panel is in category view select Hardware and Sound – Power Options. If the Control Panel is in icon view you can directly access the Power Options window.
3. Click on the “Choose what the power buttons do” option. You are now in the Power Options – System Settings pane. Here, click on the link that says “Change settings that are currently unavailable”. Using this option the Shutdown Settings (available in the same window) become active, instead of grayed out so you can change them.
4. Under Shutdown Settings you will find the option “Turn on fast startup”. This is the place where you can turn it on or off at any time.
Moreover, from the same place you can make some power options like Hibernate, Sleep and Lock available in Power and account picture menus.
Note: The Fast Startup option does not work for the Restart function. Also, the Shutdown option available in Windows 8.1’s Start button menu doesn’t benefit from the Fast Startup function. It will perform a full shutdown, whether you have Fast Startup turned on or off. When you disable Fast Startup, obviously all shutdown methods will do a regular, full shutdown instead of a hybrid one.