Comparisons · The description of System & reserved and how to display it, from Microsoft's Storage settings in Windows support page, and the state-query and state-change options and their limits from Microsoft Learn's DISM Reserved Storage Command-line Options (both read 2026-09-21)

System & reserved is eating the drive: what reserved storage is for, and how it affects the capacity you buy

Open Settings and look at Storage, and the breakdown contains an entry called System & reserved that can run to tens of gigabytes. Deleting files does not shrink it, so it reads like something broken. It is space Windows holds back for updating, and Microsoft states that when the device is low on space Windows clears it so it can be used. This guide was written on 2026-09-21 from two Microsoft documents and sets out what the space is for, where to find it in the breakdown, the command that reports its state, the limits attached to turning it off, and what to allow for when buying a small-capacity machine. No capacity was measured on hardware by this site.

Published 2026-09-21 · Updated 2026-09-21 · FaultNote editorial policy

System & reserved is eating the drive: what reserved storage is for, and how it affects the capacity you buy overview: 1. What the space is for, 2. Where to see it in the breakdown, 3. The command that reports the state, and the limits on changing it, 4. Why turning it off is not recommended here, 5. How this feeds into the capacity you buy, 6. What this guide does not say — An overview of this guide’s steps and checks, not a screenshot of the app.

Who this guide is for and what to prepare

Anyone whose storage breakdown shows a large System & reserved entry and wants to know whether it can be removed
Anyone weighing up a small-capacity laptop or tablet and trying to estimate the usable space
Anyone who runs out of free space at every update and wants the cause laid out

What you need

Confirm that Settings > System > Storage opens
Note the current free space and the size of each entry in the breakdown
Establish whether the PC is managed by an employer or school (the behaviour differs)

1. What the space is for

Microsoft's support page states the purpose: To make sure your device can successfully update and that it runs its best, Windows reserves a portion of storage space on your device for use by temporary files, caches, and other files.

It is not held indefinitely. When your device is low on space, Windows will clear reserved storage so it can be used for other processes, like a Windows update. This is the most misread part of the subject: the capacity is not lost, its use is spoken for.

A secondary effect is given as well: Reserving storage also helps keep disk space usage on your device more predictable and more stable.

Microsoft Learn puts the benefit more directly: Reserved storage increases the likelihood that Windows updates can be downloaded and installed without users having to free disk space. In other words, it exists to cut down the manual clearing-out that an update would otherwise demand.

2. Where to see it in the breakdown

The Storage page breaks usage down by category. Microsoft names Installed apps, Temporary files, System & reserved and more.

System & reserved is not always in the list to begin with. Microsoft's instruction is: To see the system reserved storage, go to the Storage settings and select Show more categories .

The same page offers Cleanup recommendations, which Microsoft describes as identifying files and applications that can safely be removed — naming temporary files including previous Windows installations, large or unused files, and rarely used apps. Looking there first is safer than going after reserved storage.

The size of each entry depends on the machine. This guide gives no figure: the sources give none, and nothing was measured here, so there is no basis for saying what size is normal.

3. The command that reports the state, and the limits on changing it

The current state can be read from an administrator Command Prompt. Microsoft Learn documents two options against an online Windows image: one that gets the state and one that sets it.

The setting side carries a stated limit: If reserved storage is in use, it may not be disabled, and the page prints the message that comes back — This operation is not supported when reserved storage is in use. Please wait for any servicing operations to complete and then try again later.

Who the feature is written for matters as much as what it does. Microsoft states Starting with the Windows 10, version 2004 the below DISM commands are available to enable IT pros to enable and disable reserved storage on demand. This is not framed as routine housekeeping on a home PC.

Managed machines are a different case again: For devices that connect directly to Windows Update (WU), reserved storage works out of the box. However, on IT managed devices using endpoint management tools such as Windows Server Update Services or Configuration Manager, reserved storage doesn't work automatically.

DISM.exe /Online /Get-ReservedStorageState

4. Why turning it off is not recommended here

This site does not recommend disabling reserved storage to gain free space. There are three reasons, and all three come from what the sources state.

First, the capacity is not permanently lost. The source states that Windows clears the reserved space and uses it when the device is low. Space gained by disabling it is largely space that would have been released when it was needed.

Second, disabling it makes it more likely that an update will require clearing space by hand. The source describes the mechanism as raising the likelihood that updates install without the user freeing disk space; turning it off pushes in the opposite direction.

Third, it cannot be disabled while in use — stated outright. Running the command in a panic once space is already tight can simply be refused. A capacity problem is better solved by the estimate in the next section than by toggling a feature.

Scroll horizontally to see the full table →

4. Why turning it off is not recommended here
What you want to do	What this guide suggests	On what basis
See what is using the space	Use Show more categories in Storage settings, then read the breakdown	The source gives the steps
Free space safely	Start from Cleanup recommendations	The source names the targets (previous installations, temporary files, large or unused files, rarely used apps)
Delete reserved storage to gain space	Not recommended. The source states it is released automatically when space is needed	The statement that it is cleared when the device is low on space
Just check the state	Use the DISM state-query option (read-only)	Documented as supported against the online image
Understand a work or school PC behaving differently	It is stated not to work automatically under management tools. Ask the administrator	The passage on IT managed devices

5. How this feeds into the capacity you buy

The figure on the box is not the space you get. This reservation sits alongside Windows itself, the recovery content and the pre-installed applications, and the smaller the drive the more that difference bites.

This guide names no number of gigabytes for the deduction. The sources give none and nothing was measured here. To estimate it, look at the free space actually reported on the Storage page of a comparable machine of the same generation.

There is a second way capacity decides things for you. A restore mechanism covered in another guide on this site is enabled by default only where the OS volume is at or above a stated size — so the capacity chosen at purchase can fix a default that is awkward to change afterwards.

Finally, separate what can be moved to an external drive from what cannot. Photos and video can go; the free space an update needs has to be on the internal drive. Adding an external disk does not solve this one.

6. What this guide does not say

It gives no figure for how much space is reserved. The sources publish none and nothing was measured here.

It gives no procedure for disabling the feature beyond querying the state. Microsoft frames the commands as an IT-professional capability, and presenting them as a way to free space on a home PC would misrepresent that.

It does not cover other operating systems, or manufacturers' own recovery partitions. Those are outside the sources.

It gives no figure for the free space an update needs. That varies by release and machine, and the sources do not state it.

Limitations and requirements

The source states that Windows clears reserved storage and uses it when the device is low on space. It is not capacity that is permanently lost.
It cannot be disabled while in use, and the source prints the message asking the user to wait for servicing operations to complete.
Microsoft documents the enable and disable commands as an IT-professional capability. Routine use of them on a home PC to gain space is not what they are framed for.
On devices managed with endpoint management tools, the mechanism is stated not to work automatically. On a work or school PC, ask the administrator.
The quoted material was read on 2026-09-21. The DISM page itself displays Last updated on 2021-09-06.

Frequently asked questions

System & reserved is huge. Is something wrong?

No. Microsoft states that Windows reserves space for temporary files, caches and other files so the device can update successfully and run at its best, and that the space is cleared when the device is low on room.

I cannot find System & reserved in the breakdown.

It is not always shown by default. Microsoft's instruction is to go to Storage settings and select Show more categories, then read the entry.

Will deleting it give me more space?

This site does not recommend it. The source states the space is released automatically when it is needed, and disabling it works against the stated purpose of installing updates without the user freeing space. It also cannot be disabled while in use.

Is there a way to just check the state?

Yes — run the DISM state-query option from an administrator Command Prompt. The code in this guide can be used as it stands; it reports the state and changes nothing.

I am told work PCs behave differently.

Microsoft states that reserved storage works out of the box on devices connecting directly to Windows Update, but does not work automatically on devices managed with tools such as Windows Server Update Services or Configuration Manager. Ask the administrator.

Sources and verification date

Sources checked: 2026-09-21. These sources support the specifications, procedures or prices discussed here. Check each source for applicable conditions and current information.

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