Restart vs shut down: what Windows Fast Startup changes

If a PC problem survives a shutdown and another start, try Restart before changing more settings. On Windows 10 and 11, a shutdown that uses Fast Startup can preserve part of Windows for the next boot. Restart takes the full boot path instead.

Turning the PC off overnight therefore does not necessarily give Windows a fresh core session. Microsoft's original Fast Startup explanation explicitly distinguishes the two routes.

Save your work first. Then choose Start > Power > Restart, let Windows return to the desktop, and check the same problem again.

What Fast Startup keeps after you shut down

Separate your signed-in apps from the Windows kernel, the operating system's core.

During a Fast Startup shutdown, Windows closes applications and signs users out. It then saves the kernel's memory image, including loaded kernel-mode drivers, to a file called Hiberfil.sys. On the next start, Windows reads that saved image back into memory. Microsoft's driver documentation describes this sequence.

Fast Startup does not preserve your open app session. Save files before using either Shut down or Restart.

The part carried across the shutdown is the Windows kernel session.

Fast Startup saves kernel state to disk for the next start. Restart takes the full boot path; both choices close the user session.

Fast Startup is designed to shorten the next boot. There is no single time saving to expect from every PC, and a faster trip to the sign-in screen does not tell you whether a fault has been cleared.

Choose the power option for the job

The options in the power menu serve different purposes. This comparison follows Microsoft's system power-state documentation .

Hibernate and Fast Startup both use a hibernation file, but they preserve different things. Hibernate retains the user's working session; Fast Startup signs the user out before saving the Windows core state.

Also check what action you actually took. Closing a laptop lid or pressing its physical power button follows that PC's configured behaviour. Microsoft's power-options guide explains those choices. Selecting Restart in Windows removes that ambiguity.

Run a useful restart test

A restart is more informative when you know what you are comparing. Keep the first check small.

1. Save your work. Finish any task that should not be interrupted, and make sure other people signed into the PC have saved theirs.
2. Name one repeatable symptom. “The headset is silent when I play this file” gives you a clearer test than “the PC is acting weird”.
3. Choose Start > Power > Restart. This is Microsoft's documented restart route for Windows 10 and 11.
4. Sign in and repeat the same action. Use the same application, file and device where practical. Check the result before changing drivers, moving cables or altering several settings.

If Windows is already asking to restart for an update, follow that request. Microsoft documents a Windows 10 case in which some updates need the full startup path to finish; an ordinary Fast Startup shutdown can leave that work pending. Its update guidance directs users to Restart. That does not mean every update fails when Fast Startup is enabled.

A restart that also installs an update changes more than the boot path. Record that fact when interpreting the result.

Worked example: a silent USB headset

Suppose your USB headset is selected as the output device, but a local music file produces no sound after you start the PC. Use that exact file as the check.

Before restarting, note the player, selected output, volume and mute status. Leave the headset connected to the same port. Restart, reopen the player and try the same file with the same output settings.

If the sound works afterwards, you have established that the behaviour changed across the restart. You have not established which component caused the original problem. Avoid turning that one success into a diagnosis.

If it is still silent, repeating the same restart gives you little new information. Move on to audio-specific checks: whether other applications can play through that output, whether another output works, and the device manufacturer's troubleshooting guidance.

If the problem returns after a later shutdown and start, record that pattern. Note whether it also returns after Restart or after waking from Sleep. Those observations help narrow the next investigation.

This comparison is easiest to interpret when you change one thing at a time. If you restart, replace the cable and install a driver together, an improvement will not tell you which action mattered.

Do you need to turn Fast Startup off?

You do not need to disable Fast Startup to use Restart's full boot path. For an isolated fault, try the restart test first.

Fast Startup is a normal Windows feature, rather than evidence of a broken shutdown. Microsoft's Windows 10 guidance says it is enabled by default on computers capable of hibernation. The relevant question is how your PC behaves, not whether every Windows installation should use the same setting.

If a problem repeatedly appears after Shut down and disappears after Restart, keep those observations for targeted device or driver troubleshooting. Include the PC model, Windows version, affected device or application, and the exact sequence that reproduces it. A temporary setting change may be part of the manufacturer's diagnosis, but the comparison alone is not a reason to make permanent changes.

Windows Fast Startup and firmware Fastboot are separate

A similar name in the BIOS or UEFI menu can refer to something else. For example, Dell's 2019 firmware configuration reference describes Fastboot in terms of which hardware and configuration checks happen during the power-on self-test.

Windows Fast Startup concerns the saved Windows kernel image. You do not need to change a firmware setting to perform the Restart test.

For the next troubleshooting attempt, record the action precisely: Restart, Shut down and power on, or wake from Sleep. Knowing which route preceded the fault makes the next check more useful.

Sources

• Microsoft: Delivering fast boot times in Windows 8 , Gabe Aul, September 2011.
• Microsoft: Distinguishing Fast Startup from Wake-from-Hibernation .
• Microsoft: System power states .
• Microsoft Support: Restart your PC .
• Microsoft Support: Shut down, sleep, or hibernate your PC .
• Microsoft: Updates may not be installed with Fast Startup in Windows 10 , KB4011287.
• Dell: Command | Configure 4.2 reference guide , April 2019, page 59.