If you want to save some space on your computer, Windows has a feature called Compact OS that can help. This guide will show you, step-by-step, how to check if Compact OS is on, and how to turn it on or off.

What is Compact OS?

Compact OS is a Windows feature that makes your system files smaller by compressing them. This helps free up disk space on your PC. When it’s turned on, Windows keeps your files compressed, and it updates them in a way that keeps saving space over time.

Learn more about Compact OS from Microsoft

Important:

• You need to be logged in as an administrator to make these changes.
• Turning Compact OS on or off can take some time — please be patient while it works.

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Step 1: Check if Compact OS is On or Off

1. Click on the Start button, type Windows Terminal, then right-click it and choose Run as administrator.
2. In the window that opens, type or paste this command and press Enter:
   
   
   compact /compactos:query
   
3. Look at the message you get:
   • If it says “Compact OS is enabled.”, then Compact OS is turned on.
   • If it says “Compact OS is disabled.”, then it is off.
4. Close the Windows Terminal window when you’re done.

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Step 2: How to Turn On Compact OS

1. Open Windows Terminal as an administrator again (see Step 1 for how).
2. Type or paste this command and press Enter:
   
   
   compact /compactos:always
   
3. Wait for the process to finish. This might take some time because Windows is compressing your files.
4. When done, you can close the window.

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Step 3: How to Turn Off Compact OS

1. Open Windows Terminal as an administrator.
2. Type or paste this command and press Enter:
   
   
   compact /compactos:never
   
3. Wait for Windows to uncompress the files. This can also take some time.
4. Close the window when it’s done.

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Summary

• You must be an administrator to make these changes.
• Compact OS helps save disk space by compressing Windows system files.
• Use simple commands in Windows Terminal to check, enable, or disable Compact OS:
  • Check status: compact /compactos:query
  • Turn on: compact /compactos:always
  • Turn off: compact /compactos:never
• Be patient — compressing or decompressing files can take some time.
• Always check the status after running the commands to confirm the change worked.

If you want a quick video walkthrough or additional help, you can visit this helpful forum thread.