Compress Windows itself with Compact OS — via Microsoft Learn

Commandlow riskNeeds adminWindows 11Windows 10

Compact OS stores the Windows system files compressed, freeing a few gigabytes on small drives. You can check its state and switch it on or off at any time with one command. Microsoft recommends it only on flash (SSD/eMMC) storage.

Takes effect right away

Command

Run in an administrator Command Prompt / Terminal window.

compact /compactos:query
compact /compactos:always

Undo

compact /compactos:never

Compressing or uncompressing takes a while. Windows Update keeps working normally on a compacted system.

Sources

compact (command reference) — by Microsoft Learn
Compact OS, single-instancing, and image optimization — by Microsoft Learn
Push-button reset FAQ — When should I use Compact OS? — by Microsoft Learn

Source reviewed: 2026-11-02
Link checked: 2026-11-02
Tested hands-on: Not by Oddbyte.Me

Oddbyte.Me hasn't tried this on every Windows build, so keep the undo handy.

compact oscompressiondisk spacessd

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