If Microsoft Defender Offline Scan is not working, first check whether it actually ran by opening Windows Security > Virus & threat protection > Protection history. To start it, use Virus & threat protection > Scan options > Microsoft Defender Antivirus (offline scan) > Scan now, after saving open work. The PC should restart, scan in Windows Recovery Environment, then restart again. If that sequence fails, the right next step depends on whether the option is missing, the restart does not happen, Windows loads normally, or an error appears.
What should happen when you start an Offline scan?
Microsoft Defender Offline is designed to run outside the normal Windows session. After you choose Scan now, the PC restarts and the scan runs in Windows Recovery Environment without loading Windows; Windows then restarts automatically when the scan finishes. Microsoft describes this as a quick scan. Save open files before starting because the restart is part of the process. Microsoft’s Windows Security guidance explains the scan flow.
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- Open Windows Security.
- Select Virus & threat protection, then Scan options.
- Select Microsoft Defender Antivirus (offline scan), then Scan now.
- Save work when prompted and allow the PC to restart.
- After Windows starts again, open Windows Security > Virus & threat protection > Protection history to review the outcome.
Check Protection history before trying the scan again
If Windows restarted and returned to the desktop without an obvious report, look in Protection history first. Microsoft identifies it as the place to see Offline scan results. A missing on-screen summary by itself does not establish that the scan failed. See Microsoft’s scan and result instructions.
Choose the next step by the symptom
The Offline scan option is missing or unavailable
Check the active security provider in Windows Security. A non-Microsoft antivirus or antimalware product can automatically make Microsoft Defender Antivirus inactive, and Microsoft recommends against running multiple real-time antivirus products simultaneously. If you use another security product, do not disable protection as a routine workaround; confirm which provider is active and follow the product’s supported removal or configuration steps if you intend to return to Defender. Microsoft says Defender should return to active mode after the other product is removed. Microsoft’s antivirus FAQ describes provider behavior.
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Selecting Scan now does not restart the PC
Apply available Windows fixes through Settings > Windows Update, restart Windows, then try the Offline scan again. Microsoft recommends installing Windows Update fixes for general malware-scan errors, although this does not identify a single cause for a failed Offline scan launch. Microsoft’s malware troubleshooting guidance covers general scan issues.
The PC restarts but returns to Windows without an apparent scan
Check Protection history before concluding the scan did not run. If there is no result and the same behavior repeats, note precisely what happened after selecting Scan now and proceed with Windows updates and symptom-based escalation rather than assuming a particular cause.
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The scan starts but is slow or cannot complete
- Close unnecessary apps. Microsoft notes that large disks and large files, including ZIP archives, can make scans take longer.
- Restart and run the scan before opening other apps, as Microsoft recommends for slow scans.
- Check that the system drive has enough free space. Low free space can prevent a scan from completing malware removal or quarantine.
These are general scan remedies, not a guaranteed fix for a failure to enter the offline environment. See Microsoft’s troubleshooting steps.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesOffline, quick, full, and custom scans are not interchangeable
Use the option that matches the problem you are trying to solve. Offline scan is the relevant choice when you need a scan outside the loaded Windows environment; quick, full, and custom scans run through Windows Security in the normal environment. Microsoft says a full scan examines every file and program, so it can take longer than a quick scan. Microsoft’s scan overview describes these choices.
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| Scan type | Where it runs | Useful distinction |
|---|---|---|
| Quick | Normal Windows session | Checks common locations. |
| Full | Normal Windows session | Examines every file and program; may take longer. |
| Custom | Normal Windows session | Lets you choose what to scan. |
| Microsoft Defender Offline | Windows Recovery Environment after a restart | Scans outside the loaded Windows environment. |
When to escalate
There is no documented universal fix for every Offline scan failure. If the steps above do not resolve it, collect the details that distinguish one failure from another:
- The exact error message, if one appears.
- Your Windows version and build.
- The security provider shown as active in Windows Security.
- What the PC does immediately after you select Scan now: no response, restart, normal Windows startup, or entry into the scan environment.
For persistent scan errors, Microsoft recommends submitting feedback through Feedback Hub and keeping Windows updated. If malware has caused broader system damage and recovery becomes necessary, review Microsoft’s Windows recovery options. Back up important files before using recovery actions that may cause data loss; recovery is an escalation, not a first-line repair for the scan feature.
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Windows 10 support status
The cited Windows Security instructions cover Windows 10 and Windows 11. Microsoft states that Windows 10 support ended on October 14, 2025. If you are still using Windows 10, take that status into account when planning ongoing security maintenance. Microsoft’s Windows security support page provides the support-status context.
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