Windows 11: What to Do When Microsoft Defender’s Quick Scan Won’t Run

Is Microsoft Defender’s Quick Scan on Windows 11 refusing to start, or halting before it’s done? Start by making sure you’re opening it from the correct spot in Windows Security. If the problem continues, reboot your PC, shut down any other antivirus software that’s active, and install Defender’s newest protection updates. Then reboot once more and try the scan again.

What Quick Scan does and why it matters

Windows 11 ships with Microsoft Defender Antivirus already built in. It guards your system against malware, including viruses, ransomware and spyware. Quick Scan focuses on the areas of your PC where malware tends to hide.

A Full Scan, by contrast, goes through every file and program on the device, which makes it far slower. Microsoft recommends Quick Scan because it finishes sooner while still giving you a good level of protection. If it stops working, you lose the simplest way to check your PC.

Run Quick Scan the correct way

Make sure you’re launching the scan from the proper screen before you try any of the fixes below.

1. Open the Start menu and search for Defender.
2. Select Device protection.
3. Click Manage in Windows Security.
4. Check that Windows Security is showing the Virus & threat protection page. If it isn’t, pick that option from the menu on the left.
5. Click Quick scan.

The scan should begin and display an estimate of how long it will take. Most scans finish in less than two minutes, but a PC holding a large amount of data may take longer.

Restart your PC

If Quick Scan still won’t run, reboot your computer and go through the steps above again. This sometimes clears up the issue, but it doesn’t work every time.

Close any other antivirus program

A second antivirus product running alongside Defender can interfere with it. To check for one:

1. Open Windows Security and go to Virus & threat protection.
2. Under Who’s protecting me?, select Manage providers.
3. Look through the list for any other known antivirus provider.
4. If one shows up, right-click its icon and choose Exit or Close.
5. Run Quick scan again.

Once the Quick Scan is done, you can switch the other antivirus back on if you like.

Install the latest Defender protection updates

If Microsoft Defender Antivirus has fallen behind, installing its latest protection updates brings in current security intelligence along with engine and platform updates. Automatic updates don’t always download, so a manual check confirms that the newest patches and bug fixes are installed.

1. In Windows Security, on the Virus & threat protection page, click Protection updates.
2. Click the gray Check for updates button.
3. Wait for Windows to finish checking, and follow any instructions that appear on screen.
4. Look for a new update and confirm that the Version created on date has changed.
5. Restart your PC.
6. Run Quick scan again.

Once your PC has restarted, Quick Scan should work normally.

Frequently asked questions

How long should a Windows Defender Quick Scan take?

Most scans finish in less than two minutes. If your Windows 11 PC holds a large amount of data, it may take longer.

What’s the difference between Quick Scan and Full Scan?

Full Scan goes through every file and program on your device, while Quick Scan only checks the places where malware most often hides. Quick Scan is the recommended choice because it’s faster and still gives you a good level of protection.

Do I have to keep my other antivirus turned off?

No. It only needs to be closed while the Quick Scan is running, and you can switch it back on when the scan is finished.