Learn how to roll back or uninstall the signature definitions and engine files for Windows Defender.
If you’re having a problem updating Windows Defender’s definitions try rolling back the definitions to the last set or completely uninstall all signature definitions and engine files.
Roll Back the Signature Definitions
- Click the Start orb, All Programs, Accessories, and then right-click Command Prompt and select Run as Administrator to start an elevated command prompt.
- Type C:\Program Files\Windows Defender\MpCmdRun.exe –RemoveDefinitions in the command prompt.
- Press Enter on your keyboard.
Windows Defender’s signature definitions will be rolled back to last set. You can try re-downloading the latest signature definitions.
Uninstall All Signature Definitions and Engine Updates
- Click the Start orb, All Programs, Accessories, and then right-click Command Prompt and select Run as Administrator to start an elevated command prompt.
- Type C:\Program Files\Windows Defender\MpCmdRun.exe –RemoveDefinitions –All in the command prompt.
- Press Enter on your keyboard.
Windows Defender’s default signature definitions and engine will be loaded. You can re-download new signature definitions and engine updates now.
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