How does one do an offline scan? I tried it once but nothing happened. I just now tried this Head to Settings > Update & Security > Windows Defender. Scroll down and click the “Scan Offline” button under Windows Defender Offline. After you click this button, your computer will automatically reboot and begin scanning your PC for malware. The scan may take up to fifteen minutes.Aug 9, 2016 But got to Scroll down & click the "Scan Offline" but its not there.