Free up Windows 10 Disk Space with Compact OS

Martin Brinkmann
Jul 28, 2016
Updated • Jul 5, 2017
Windows, Windows 10
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16

Compact OS is a new command line tool that Microsoft introduced in the Windows 10 operating system in an effort to reduce the system's disk footprint.

Probably the biggest change to previous versions of Windows in this regard is that Windows 10 does not need recovery images anymore, as the operating system will use existing files for that instead.

Compact OS is a new compression mechanism which takes files of the operating system and puts them in a (hidden) compressed container.

There is a lot that you can do with Compact OS, especially when it comes to optimizing and deploying images.

What's probably most interesting from an end-user's perspective is that you may change from a non-compacted to a compacted OS on a running system.

Free up Windows 10 Disk Space with Compact OS

If you do that, you may free up several Gigabytes of storage on the hard drive because of it. Mileage may vary but I have yet to come upon a system where the Compact OS operation would not free up at least 2 Gigabytes of space.

2 Gigabytes may not be much depending on available hard drive space. Running the operation makes sense if Windows is installed on a partition with little hard drive space, or a Solid State Drive that is low on space.

All commands are run from an elevated command prompt.

  1. Tap on the Windows-key.
  2. Type cmd.exe
  3. Hold down Shift and CTRL.
  4. Select the Command Prompt result to open an elevated command prompt.

Determine the state of OS binaries

compact os query

Before you do any compacting, you may want to determine the current state of OS binaries to find out whether the OS is already compressed.

Run the following command to determine that:

  • compact.exe /q

The command line tool returns information about the state. This includes how many files are compressed or not compressed, the compression ratio, and how many bytes of data are stored in the compressed container.

If the compression ratio is 1,0 to 1 or close to that, then the OS is not compressed.

Compressing the OS binaries to save up disk space in Windows 10

compact os always

Compression may impact performance under certain circumstances but it should not be noticeable on most systems.

Please note that you can go back to an uncompressed state at any point in time if you notice issues after compressing the OS. Also, to be on the safe side, it is recommended to back up important data before you continue.

Run the following command to compress OS binaries:

  • compact.exe /CompactOS:always

The operation may take several minutes to complete (on some systems 20 or more minutes). The amount of space you save depends on a number of factors. A test on the latest Insider Build installation of Windows 10 saved more than 2 Gigabyte of disk space after the compression.

To revert the change later on, run the following command to uncompress the data:

  • compact.exe /CompactOS:never

The operation does not take as long as the compression usually. Windows will occupy more disk space afterwards though so keep that in mind.

Now Read: Run Disk Cleanup to free up lots of space on Windows 10

Summary
Free up Windows 10 Disk Space with Compact OS
Article Name
Free up Windows 10 Disk Space with Compact OS
Description
Find out how to save disk space on the main Microsoft Windows 10 hard drive by running the command line tool compact OS to compress files.
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Ghacks Technology News
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Comments

  1. Dan Donx said on January 15, 2023 at 10:29 am
    Reply

    What mental age of reader are you targeting with the first sentence? 10?

    Why not write an article on how to *avoid* upgrading from W10 to W11. Analogous to those like me who avoided upgrading from 7 to 10 for as long as possible.

    If your paymaster Microsoft permits it, of course.

  2. Dexter said on January 15, 2023 at 11:14 am
    Reply

    5. Rufus
    6. Ventoy

    PS. I hate reading these “SEO optimized” articles.

    1. cdr said on January 15, 2023 at 3:32 pm
      Reply

      I used Rufus to create an installer for a 6th gen intel i5 that had MBR. It upgraded using Setup. No issues except for Win 11 always prompting me to replace my local account. Still using Win 10 Pro on all my other PCs to avoid the bullying.

  3. sv said on January 15, 2023 at 6:40 pm
    Reply

    bit pointless to upgrade for the sake of upgrading as you never know when you’ll get locked out because ms might suddenly not provide updates to unsupported systems.

    ps…. time travelling?
    written. Jan 15, 2023
    Updated • Jan 13, 2023

    1. Martin Brinkmann said on January 16, 2023 at 5:49 am
      Reply

      This happens when you schedule a post in WordPress and update it before setting the publication date.

  4. Anonymous said on January 16, 2023 at 8:24 am
    Reply

    Anyone willing to downgrade to this awful OS must like inflicting themselves with harm.

  5. basingstoke said on January 16, 2023 at 11:18 am
    Reply

    I have become convinced now that anybody who has no qualms with using Windows 11/10 must fit into one of the following brackets:

    1) Too young to remember a time before W10 and W11 (doesn’t know better)

    2) Wants to play the latest games on their PC above anything else (or deeply needs some software which already dropped W7 support)

    3) Doesn’t know too much about how computers work, worried that they’d be absolutely lost and in trouble without the “”latest security””

    4) Microsoft apologist that tries to justify that the latest “features” and “changes” are actually a good thing, that improve Windows

    5) Uses their computer to do a bare minimum of like 3 different things, browse web, check emails, etc, so really doesn’t fuss

    Obviously that doesn’t cover everyone, there’s also the category that:

    6) Actually liked W7 more than 10, and held out as long as possible before switching, begrudgingly uses 10 now

    Have I missed any group off this list?

    1. Heinz Strunk said on September 19, 2023 at 3:57 pm
      Reply

      You have missed in this group just about any professional user that uses business software like CAD programs or ERP Programs which are 99% of all professional users from this list.

      Linux doesn’t help anyone who is not a linux kid and apple is just a fancy facebook machine.

  6. ilev said on August 24, 2023 at 7:34 pm
    Reply

    Microsoft has removed KB5029351 update

    1. EP said on August 24, 2023 at 9:21 pm
      Reply

      only from windows update though
      KB5029351 is still available from the ms update catalog site

  7. Anonymous said on August 24, 2023 at 11:05 pm
    Reply

    1. This update is labaled as PREVIEW if it causes issues to unintelligent people, then they shouldn’t have allowed Preview updates ot install.

    2. I have installed it in a 11 years old computer, and no problems at all.

    3. Making a big drama over a bluescreen for an updated labeled as preview is ridiculous.

    This is probably another BS internet drama where people ran programs and scripts that modified the registry until they broke Windows, just for removing stuff that they weren’t even using just for the sake of it.
    Maybe people should stop playing geeks and actually either use Windows 10 or Windows 11, but don’t try to modify things just for the sake of it.

    Sometimes removing or stopping things (like defender is a perfect example) only need intelligence, not scripts or 3rd party programs that might mess with windows.

  8. john said on August 24, 2023 at 11:17 pm
    Reply

    Windows 11 was a pointless release, it was just created because some of the Windows team wanted to boost sales with some sort of new and improved Windows 10. Instead, Microsoft cannot support one version well let alone two.

    1. John G. said on August 25, 2023 at 12:08 pm
      Reply

      Windows 11 is the worst ugly shame by Microsoft ever. They should release with every new W11 version a complete free version of Starallback inside just to make this sh** OS functionally again.

  9. EP said on August 25, 2023 at 3:10 pm
    Reply

    motherboard maker MSI has recently released a statement regarding the “unsupported processor” blue screen error for their boards using Intel 600/700 series chipsets & to avoid the KB5029351 Win11 update:
    https://www.msi.com/news/detail/MSI-On–UNSUPPORTED-PROCESSOR–Error-Message-of-Windows-11-Update-KB5029351-Preview-142215

  10. EP said on August 29, 2023 at 7:32 pm
    Reply

    check out the following recent articles:

    Neowin – Microsoft puts little blame on its Windows update after UNSUPPORTED PROCESSOR BSOD bug:
    https://www.neowin.net/news/microsoft-puts-little-blame-on-its-windows-update-after-unsupported-processor-bsod-bug/

    BleepingComputer – Microsoft blames ‘unsupported processor’ blue screens on OEM vendors:
    https://www.bleepingcomputer.com/news/microsoft/microsoft-blames-unsupported-processor-blue-screens-on-oem-vendors/

  11. Leonard Britvolli said on August 30, 2023 at 10:33 pm
    Reply

    While there may be changes or updates to the Windows 10 Store for Business and Education in the future, it is premature to conclude that it will be discontinued based solely on rumors.

  12. sembrador said on September 5, 2023 at 9:32 pm
    Reply

    My advice, I left win 15 years ago. Now I’m a happy linux user (linuxmint) but there is Centos, Fedora, Ubuntu depending on your needs.

  13. EP said on September 6, 2023 at 11:55 am
    Reply

    motherboard maker MSI has recently released new BIOS/firmware updates for their Intel 600 & 700 series motherboards to fix the “UNSUPPORTED_PROCESSOR” problem (Sept. 6):

    https://www.msi.com/news/detail/Updated-BIOS-fixes-Error-Message–UNSUPPORTED-PROCESSOR–caused-BSOD-on-MSI-s-Intel-700-and-600-Series-Motherboards-142277

  14. Raphael Benzo said on September 24, 2023 at 9:52 pm
    Reply

    I try to disable the Diagnostics Tracking Service (Connected Devices Platform User Services) but it wont let me disable it, any help will be greatly appreciated.
    Tank you for your help

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