How to Check & Disable CompactOS on Windows 10
Windows can run in a compressed state called CompactOS. You can enable it manually, or Windows may turn it on during setup or a feature update—often without an obvious prompt. In some cases, this compression can make a system with very little free space feel slower after an update. Here’s how to check, disable, or enable CompactOS on Windows 10 (these commands also work on Windows 11).
Note on updates & free space: Starting with Windows 10 version 1903, Microsoft introduced Reserved Storage which automatically sets aside several GB for updates and temp files. If your device has Reserved Storage enabled and adequate free space, you can usually disable CompactOS without risking update failures.
Check compactOS state
Open Command Prompt (Admin) and run:
compact /compactos:query
You’ll see whether the OS is currently in a compact state and the reason (e.g., enabled automatically by Windows because it “thinks it’s best” for your device, or set by an administrator). On some systems, Windows may report that CompactOS isn’t enabled now but could be enabled automatically if disk space becomes tight later.
Disable compactOS
Disabling CompactOS requires admin rights and will increase the space Windows uses on your system drive. Expect Windows to take several GB more space after you turn compression off.
compact /compactos:never
The process can take a while (several minutes or longer) depending on your CPU, storage speed, and how much has to be decompressed. You can continue using the PC, but performance may dip until it finishes.
Before you disable it: Make sure you have enough free space for future updates. With Windows 10 1903+ and Windows 11, Reserved Storage typically holds back ~7GB (varies by device and language packs) to help updates succeed. If Reserved Storage is off and your drive is tight on space, leaving CompactOS enabled may be safer.
Enable compactOS
To turn CompactOS on (useful on low-capacity devices), run Command Prompt (Admin) and use:
compact /compactOS:always
This compresses Windows system files to save space. Microsoft’s guidance indicates the savings are typically a couple of GB on most systems, and can be higher alongside other optimizations. Compression work takes time; allow it to finish before judging performance.
Heads-up on performance: On modern CPUs and SSDs the impact is usually small, but devices with very low-end processors or under heavy CPU load can feel slower because the OS has to decompress files as it uses them.
FAQs & quick notes
It stores and runs Windows system files in compressed form to reduce disk footprint. See Microsoft’s overview of Compact OS.
It varies by edition, architecture, and language packs. Microsoft documentation shows savings commonly around 1.5–3.7GB and higher with additional optimizations. Details: Compact OS, single-instancing, and image optimization.
No. CompactOS targets Windows system binaries and apps; standard NTFS compression is a separate, file/folder-level feature. Command reference: compact command.
Yes—the same compact /compactos:query|always|never options are supported.
Not by itself, as long as you maintain sufficient free space. Devices with Reserved Storage are less likely to encounter low-space update errors.
Windows can enable it automatically based on heuristics at install/upgrade time (for example, language packs or prior free space). You can override it with the commands above.
References
- Microsoft Docs: Compact OS, single-instancing, and image optimization
- Microsoft Docs:
compactcommand reference - Microsoft Tech Community: Managing Reserved Storage
What’s New in This Update
- Clarified typical space savings and performance trade-offs using Microsoft’s current documentation.
- Added guidance for devices with Reserved Storage (Windows 10 1903+ / Windows 11) so updates aren’t blocked after disabling CompactOS.
- Confirmed that the same
compact /compactoscommands apply on Windows 11. - Expanded timing expectations (decompression/compression can take longer on slower CPUs or disks).
- Added a References section with up-to-date Microsoft resources.
Last updated: 2025-10-21
