I am quite confused. I thought Windows 10 “fast boot” was hibernation and default “shutdown” behavior. I thought Windows 10 startup times were faster because of hibernation shortcutting the real boot sequence.
Windows 8 and later enable “fast boot” by default which, on shutdown, logs the user out of the current session and then hibernates the logged out state of the OS by writing the RAM contents to disk.
“Full” hibernation is still there, it’s just disabled by default in the UI but not on the OS level.
There’s also this “hybrid sleep” concept introduced since Vista where an OS would go from Sleep state to Hibernate automatically after 180 minutes of Sleep (IIRC, also can be overridden by the OEM) to save the laptop battery further since after the laptop hibernates it’s effectively off.
It’s really confusing and a hell to troubleshoot if something goes wrong. I think Microsoft was trying to apply smart decisions on the OS level _for_ the user but there’s no real indication of what’s actually happening with the system. The naming doesn’t help either, especially after “Modern Sleep” has been introduced.
EDIT: I decided to check myself because I wasn’t sure and it turns out I was indeed wrong. “Hybrid Sleep” is actually about a device going to Sleep and Hibernate simultaneously - it’s so that you can still resume from the hibernated image on the disk in case battery dies while in Sleep. At the same time, you can resume from Sleep right away even before parallel hibernation is finished. I think the intention is that you kinda get the best of both worlds here.
The behavior of going to sleep to hibernate after some time which I’ve described originally is actually something that was there since at least Windows XP.
