“What is the difference between sleep, hybrid sleep, and hibernate on a laptop?”

(Answer requested by Shreya Mehta)

In sleep mode (sometimes called suspend), your PC goes into a low-power state, consuming just enough electricity to keep the RAM contents intact; to monitor for system events (such as a key- or mouse-click, or closing the lid on a laptop); and to run similar low-power processes. The major advantage of standard sleep mode is that, when the PC wakes up, it can pick up from where it was almost instantly. The downside to standard sleep is that if anything interrupts the power supply to the sleeping PC, the contents of RAM (including any unsaved files) will be lost, and the PC will not be able to resume normally upon wake-up.

Hibernation writes the entire contents of RAM and the exact state of your PC’s CPU into a hidden hibernation file on the hard drive; then the PC shuts off completely. When a PC awakens from hibernation, Windows uses the contents of the hibernation file to put the system RAM and CPU back into the exact state they were in when hibernation began. Because this usually involves manipulating several GB of data, this process is not instantaneous — it usually takes at least a few seconds. But when the PC fully re-awakens, it can pick up from where it left off. Hibernation is more robust than sleep because the PC is totally off: Even if you unplug the PC or remove its battery, the data is safe on the inert hard drive.

Hybrid sleep combines standard sleep and hibernation in a three-step process. First, when hybrid sleep commences, the system prepares as if it were going to hibernate; the RAM and CPU contents are fully written to the hard drive. But in the second step, instead of shutting down completely, the PC then goes into sleep mode. This way, the PC can wake up instantly (like standard sleep); but with the robustness of hibernation, in that a power-loss or total shut down won’t cause trouble (because all data is safely stored in the hibernation file on the hard drive). The third step commences if the PC remains undisturbed in hybrid sleep for long enough: The sleep mode portion terminates, and the PC then enters full, standard hibernation.

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