Windows has three startup modes: what Fast Startup actually loads
Turn it off and on again, and the fault is still there. Behind that is a fact about Windows: starting up is not one thing. Microsoft names three startup modes and states that a fast startup is a different operation from a cold startup — specifically, that it loads the hibernation file rather than rebuilding the kernel image and re-enumerating devices. This guide was written on 2026-09-21 from two Microsoft pages, and it keeps what those pages state separate from what this site could not confirm. Nothing was tested on hardware.
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Who this guide is for and what to prepare
- People whose fault survives switching the machine off and on
- People who want to know what the Fast Startup setting actually does
- People deciding whether to turn it off, who want something to decide on
What you need
- Note which way of shutting down the fault survives
- Be able to open Power Options in Control Panel
- Be able to put any setting back the way it was
1. Microsoft counts three
The driver documentation opens with it: There are three startup modes in Windows: Cold (traditional) Wake-from-hibernation Fast (combines first two, introduced in Windows 8)
Cold, wake-from-hibernation, and fast — the last described as combining the first two and introduced in Windows 8. In everyday speech all three are just starting the machine; in Microsoft's terms they are different operations.
That matters for diagnosis, because starting again does not always reload the same things.
2. What gets rebuilt differs
On a cold startup: During a cold startup, the boot loader constructs a kernel memory image by loading the sections of the Windows kernel file into memory and linking them. Next, the kernel configures core system functions, enumerates the devices attached to the computer, and loads drivers for them.
The kernel image is built, core functions configured, attached devices enumerated, drivers loaded.
Fast startup is described against that: In contrast, a fast startup simply loads the hibernation file (Hiberfil.sys) into memory. A fast startup tends to take significantly less time than a cold startup.
The reason it is quick and the reason some things are not reloaded are the same reason. It is reading back a saved kernel state rather than constructing one.
Scroll horizontally to see the full table →
| Startup mode | What Microsoft states, summarised |
|---|---|
| Cold (traditional) | The boot loader constructs a kernel memory image; the kernel configures core system functions, enumerates attached devices and loads their drivers |
| Wake-from-hibernation | Named as one of the three startup modes |
| Fast (introduced in Windows 8) | Combines the first two. Simply loads the hibernation file (Hiberfil.sys) into memory, and tends to take significantly less time than a cold startup |
3. Which one an ordinary shutdown leads to
A second source fills that in. Microsoft's Wake on LAN support article states: In Windows 10, the default shutdown behavior puts the system into the hybrid shutdown (also known as Fast Startup) state (S4).
And describes that state: In Windows 10, hybrid shutdown (also known as Fast Startup) (S4) stops user sessions but lets the contents of kernel sessions be written to the hard disk.
Put the two together and the startup that follows a default shutdown is the kind that reads a kernel state back. What a reader thinks of as turning it off and on again is not, in Microsoft's terms, a cold startup.
4. What this site could not confirm
There is a well-known next sentence to this subject: so choose Restart instead, and you get a cold startup. This guide does not write it. Neither page read here says which startup mode a restart produces.
Microsoft support pages were searched for it; every URL tried returned 404, and no statement was found. Without one, saying restart gives you a cold startup would take this article outside the sources it rests on.
What can be said instead is still useful. The two quoted passages establish that different amounts get rebuilt depending on the startup mode, so trying a different way of shutting down is a grounded thing to do about a persistent fault. What this site cannot do is tell you which button maps to which mode.
In practice, noting whether the fault survives each way of shutting down is itself diagnostic information. This guide simply does not fill the mechanism in by guessing.
05. Whether to turn it off
The steps to disable Fast Startup are in Microsoft's Wake on LAN article: Power Options in Control Panel, Choose what the power buttons do, clear Turn on fast startup (recommended), Save Settings.
But the same article puts this immediately before them: We don't recommend that you disable the hybrid shutdown (S4) state. This guide does not present it as a recommendation either.
What you would be trading, from the sources: you lose the tendency to take significantly less time to start, and gain a configuration in which the kernel state is rebuilt at every shutdown. Which is worth more depends on how the machine is used.
This setting also bears on remote wake. This site covers Microsoft's statement that Wake on LAN from a normal shutdown is unsupported in a separate guide.
Scroll horizontally to see the full table →
| Consideration | What the sources support | What this guide will not say |
|---|---|---|
| Startup speed | A fast startup is stated to take significantly less time than a cold startup | A figure in seconds. Nothing was measured |
| Whether a fault survives | That different amounts are rebuilt per startup mode is clear from the quoted passages | Which way of shutting down maps to which mode; restart could not be confirmed |
| Microsoft's own position | Disabling hybrid shutdown is stated as not recommended | Why, in detail. The article offers no further explanation |
| The effect on remote wake | Covered separately: WOL from a normal shutdown is stated unsupported | That disabling it will certainly make remote wake work |
Limitations and requirements
- Nothing was tested on hardware for this guide. The operations and conditions quoted are from Microsoft's published documents.
- This guide does not say that choosing Restart produces a cold startup. Neither source says so and this site could not confirm it.
- Microsoft does not recommend disabling hybrid shutdown (Fast Startup), and neither does this guide.
- The wording quoted was read on 2026-09-21. The startup-mode source is driver developer documentation, not a user-facing procedure.
Frequently asked questions
Is starting Windows not one single thing?
Microsoft names three modes: cold (traditional), wake-from-hibernation, and fast, the last described as combining the first two and introduced in Windows 8.
What does a fast startup actually do?
Microsoft states that it simply loads the hibernation file (Hiberfil.sys) into memory, in contrast with a cold startup, where the boot loader constructs a kernel memory image and the kernel enumerates attached devices and loads their drivers.
I turned it off and on again and the fault is still there.
Microsoft states that the Windows 10 default shutdown enters the hybrid shutdown (Fast Startup) state, and the startup that follows reads a kernel state back rather than rebuilding it. Which way of shutting down produces a cold startup is something this site could not confirm.
Does Restart give a cold startup?
This guide does not say so. Neither source read here states which startup mode a restart produces, and no such statement was found.
Should I disable Fast Startup?
Microsoft states that disabling hybrid shutdown is not recommended, and this guide does not recommend it either. The steps are on Microsoft's page, and the trade is against startup time.
Sources and verification date
Sources checked: . These sources support the specifications, procedures or prices discussed here. Check each source for applicable conditions and current information.
- Microsoft: Distinguishing Fast Startup from Wake-from-Hibernation. States that there are three startup modes in Windows — Cold (traditional), Wake-from-hibernation, and Fast (combines first two, introduced in Windows 8); that during a cold startup the boot loader constructs a kernel memory image, and the kernel configures core system functions, enumerates attached devices and loads drivers for them; and that in contrast a fast startup simply loads the hibernation file (Hiberfil.sys) into memory and tends to take significantly less time than a cold startup. Read 2026-09-21 ↗
- Microsoft: How to enable Wake on LAN (KB 2776718). States that the Windows 10 default shutdown behaviour puts the system into the hybrid shutdown (also known as Fast Startup) state (S4); that hybrid shutdown stops user sessions but lets the contents of kernel sessions be written to the hard disk; the steps for disabling Fast Startup; and We don't recommend that you disable the hybrid shutdown (S4) state. Read 2026-09-21 ↗
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