Microsoft Safety Scanner: Free On-Demand Malware Check

Sometimes you want a second opinion without installing a whole new antivirus. Microsoft Safety Scanner is a single executable that you download, run once and delete. It looks for malware and tries to undo changes made by any threats it finds.

How it differs from an antivirus

• Manual only: It scans when you start it, never in the background.
• Short shelf life: Each download expires 10 days later. For a scan with fresh definitions, download it again; Microsoft recommends doing so before every scan.
• Portable: It is not installed, does not appear in the Start menu and leaves no desktop icon, so remember where you saved it.
• Not a replacement: Microsoft says it does not replace your anti-malware product. For ongoing protection, Microsoft Defender Antivirus is built into Windows 10 and 11.

Running a scan

1. Use the Download button to reach the official Microsoft Learn page, then pick the 32-bit or 64-bit file to match your Windows.
2. Open the downloaded file (msert.exe by default) and accept the prompts.
3. Choose the scan type you want and start it.
4. Review the results on screen. A detailed log is written to %SYSTEMROOT%\debug\msert.log.
5. When you are done, delete the executable to remove the tool.

Compatibility notes

The tool works on Windows 11, 10, 8.1, 8 and 7, and on Windows Server 2019, 2016, 2012 R2, 2012 and 2008 R2. It is signed only with SHA-2, so very old Windows 7 installations need the SHA-2 code signing update before it will run.