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Enable Hibernation and Tune Fast Startup

Hibernation writes memory to disk and switches off; Fast Startup only half-shuts down. Both are one command away and both cost something.

by@guidox updated:10/31/26 time:15 min level:Beginner tested on:Windows 11 24H2 works on:Windows 10, Windows 11 tools:Admin terminal
TL;DR

Turn hibernation on with **powercfg /hibernate on**, cap the file with **powercfg /h /size**, and switch **Fast Startup** off if you dual-boot or rely on **Wake-on-LAN**.

Before you start

Requirements

  • Admin terminal
  • Space on the system drive
  • Five minutes
Step by step

Instructions

01

Ask what the machine supports

The power configuration lists sleep, hibernate and fast startup and names what blocks each one. Reading it first avoids chasing a setting that the firmware does not offer.

powercfg /a
02

Turn hibernation on

One command enables the feature and creates the file that stores the memory image. Without it, the hibernate entry never appears in the power menu.

powercfg /hibernate on
03

Decide how large the file should be

The default takes about 40 percent of installed memory. A smaller file saves disk space but limits how much of a full session can be stored; reduced mode is enough for fast startup alone.

powercfg /h /size 40
powercfg /h /type reduced
tipOn a 32 GB machine the default file is around 13 GB. Check free space before you enable, not after.
04

Understand what Fast Startup really does

It writes the kernel session to disk on shutdown and reloads it on start. That makes boot faster, but it also means a shutdown is not a full driver reset, which breaks dual-boot and some updates.

Control Panel > Power Options > Choose what the power buttons do
⚠ warningWake-on-LAN from a full shutdown usually fails with Fast Startup on. Disable it before you debug the network card.
05

Test hibernate from the menu

Hibernate through the power menu rather than by closing the lid; the lid action is a separate setting. On resume, the session should return exactly where it was, with the network up.

Alt+F4 > Hibernate
06

Check the disk cost once

The file is hidden in the root of the system drive. Confirm the size matches what you configured, and remember that deleting it by hand does not disable the feature.

dir /a:hs C:\iberfil.sys
Troubleshooting

Common issues

The hibernate entry never appears

The firmware does not expose the state, or a policy hides the menu. Run powercfg /a to see which of the two it is.

powercfg refuses the smaller size

Fast startup needs a minimum file. Use reduced mode, or turn fast startup off before shrinking it.

Resume takes almost as long as a boot

A slow disk or a large session. On a hard drive this is normal; on an SSD check the drive's health.

Shutdown leaves the machine in a strange state

That is fast startup, not a real shutdown. Hold Shift while clicking Shut down for a full one.

FAQ

Frequently asked

Hibernate or sleep?

Sleep keeps memory powered and resumes in a second; hibernate survives a power cut and takes longer.

Does hibernation wear out an SSD?

The write per cycle is large but rare. For normal use the difference is not measurable.

How to undo this

Run **powercfg /hibernate off** to remove the feature and delete the file. Re-enable **Fast Startup** in the same power options page if you switched it off.

Changelog · 1 entry
  1. 2026-10-31
    First version
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