Windows Defender Error 0x80073b01: Fixes That Work

Windows Defender error 0x80073b01 usually appears when you try to open the Windows Security app or run a scan, and it means the security service isn’t responding or the app’s files are corrupted. This guide explains the most common causes and provides step-by-step fixes that resolve the issue on current versions of Windows 10 and Windows 11.

What Does Error 0x80073b01 Mean?

The error code 0x80073b01 is a Windows error that typically translates to “The application is not installed correctly” or “The service cannot be started”. In the context of Windows Defender (now called Microsoft Defender), it often appears when the Security Center service (SecurityHealthService) fails to start, or when the Windows Security app itself has become corrupted or its dependencies are broken.

You might see this error when:

• Opening the Windows Security app from the Start menu or taskbar.
• Running a quick or full scan from the Windows Security interface.
• Clicking on any tab inside Windows Security (like Virus & threat protection).
• After a Windows update that partially failed or was interrupted.

The error is not a sign that your PC is infected; it’s a system-level glitch that prevents Defender from running properly. Fortunately, it’s fixable with built-in Windows tools.

Why Does This Error Happen?

Several underlying issues can trigger 0x80073b01. The most common are:

• Corrupted Windows Security app files – The app’s internal components may be damaged, often after a failed update or a third-party security tool was uninstalled incorrectly.
• Disabled or stopped services – Windows Defender relies on several background services like SecurityHealthService, WinDefend, and WdNisSvc. If any of these are disabled, the error appears.
• Group Policy or registry interference – Sometimes a previous antivirus or a tweak tool disables Defender via registry keys or policy settings, even if you didn’t intend to.
• Outdated or broken Windows Update components – Defender definitions and the app itself are updated through Windows Update; a broken update pipeline can leave the app in a bad state.
• Third-party antivirus conflicts – If you recently installed another antivirus and then removed it, leftover drivers or services can block Defender.

How to Fix Error 0x80073b01 (Step-by-Step)

Try these fixes in order. Most users resolve the issue with the first two steps. You’ll need administrator rights for all of them.

1. Restart the Security Center Service

1. Press Win + R, type services.msc, and press Enter.
2. Scroll down to Security Center (or SecurityHealthService).
3. Right-click it and select Restart. If it’s not running, select Start.
4. Set its Startup type to Automatic (right-click → Properties → Startup type).
5. Close the window and try opening Windows Security again.

2. Re-register the Windows Security App

This resets the app’s installation without removing your data. Open PowerShell as administrator (right-click Start → Terminal (Admin) or Windows PowerShell (Admin)) and run:

Get-AppxPackage Microsoft.Windows.SecHealthUI | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

Wait for it to finish, then restart your PC. This is the most effective fix for corrupted app files.

3. Run SFC and DISM

System file corruption can cause this error. Run these commands in the same admin terminal:

1. Type sfc /scannow and press Enter. Wait for it to complete (may take 15-20 minutes).
2. Then run DISM /Online /Cleanup-Image /RestoreHealth and press Enter. This repairs Windows image files.
3. Restart your PC after both complete.

4. Check for Conflicting Policies

If Defender was disabled via Group Policy or registry, it won’t start. Open the Group Policy Editor (Win + R → gpedit.msc) and navigate to:

Computer Configuration → Administrative Templates → Windows Components → Microsoft Defender Antivirus

Double-click Turn off Microsoft Defender Antivirus and set it to Not Configured. If you don’t have Group Policy (Windows Home), check the registry:

1. Open Regedit (Win + R → regedit).
2. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender.
3. If there’s a value named DisableAntiSpyware, delete it or set its value to 0.
4. Restart your PC.

5. Run Windows Update

Go to Settings → Windows Update and click Check for updates. Install any pending updates, including Defender definition updates. Restart after updating.

6. Reset Windows Security via Settings

1. Open Settings → Apps → Installed apps.
2. Search for Windows Security.
3. Click the three-dot menu and select Advanced options.
4. Click Reset (and optionally Repair first). This clears the app’s data and re-registers it.

What If the Error Persists?

If none of the above work, the issue may be more deeply rooted. Here are a few extra steps you can try:

• Perform a clean boot – Disable all non-Microsoft services and startup items to see if a third-party app is interfering. Use msconfig (System Configuration) and uncheck all non-Microsoft services, then restart.
• Use the Windows Security Troubleshooter – Download the official “Windows Security” troubleshooter from Microsoft’s support site (search for “Windows Security troubleshooter”). It automatically detects and fixes common issues.
• Repair Windows with an in-place upgrade – Run the Windows 10/11 installation media and choose “Keep files and apps”. This reinstalls the OS without losing your data, and often resolves stubborn Defender errors.
• Check for third-party antivirus leftovers – If you recently uninstalled a third-party antivirus, use the vendor’s dedicated removal tool (e.g., McAfee Removal Tool, Norton Removal Tool) to clean up leftover drivers.

Common Misconceptions About This Error

One common myth is that error 0x80073b01 means your PC is infected or that Defender has been disabled by malware. While malware can disable Defender, this error is usually just a service or app glitch. Another misconception is that you need to reinstall Windows to fix it – that’s rarely necessary. The error is also not related to your Microsoft account or licensing; it’s purely a local system issue.

Also, note that this error is different from 0x80070005 (access denied) or 0x80070422 (service cannot be started). The fix methods are different, so don’t confuse them.

How to Prevent This Error in the Future

• Always install Windows updates – Regularly updating keeps Defender components healthy.
• Avoid third-party tweaking tools – Many “debloat” or “privacy” tools disable Defender permanently, which can cause this error later.
• Uninstall antivirus properly – Use the vendor’s official removal tool, not just “Uninstall” from Settings.
• Run periodic SFC scans – If you notice system instability, running sfc /scannow monthly can catch corruption early.

Frequently Asked Questions

Will I lose my files if I reset Windows Security?

No. Resetting the Windows Security app only clears its settings and re-registers the app. Your personal files, documents, and other apps are untouched. However, you may need to reconfigure any custom security settings after the reset.

Is this error a sign of a virus?

Not necessarily. While malware can cause Defender to malfunction, the 0x80073b01 error is most often due to a corrupted app or a stopped service. If you’re concerned, run a scan with another security tool or boot into Safe Mode and run a scan with the built-in Defender offline scan (if accessible).

Can I just disable Defender instead of fixing it?

You can, but it’s not recommended. Disabling Defender leaves your PC without real-time protection. If you have another antivirus installed, it’s fine to disable Defender, but if you don’t, fix it instead. If you must disable it, use Group Policy or registry, but remember to re-enable it later.

Does this error affect Windows 11 and Windows 10 the same way?

Yes, the error and fixes are essentially identical on both operating systems. The menu paths may differ slightly (e.g., Settings → Apps vs. Settings → Apps & features), but the underlying commands and services are the same.

Why does the error keep coming back after I fix it?

If the error recurs, there’s likely an underlying cause like a third-party service that re-disables Defender, or a corrupted Windows Update component. Try the clean boot method to identify the culprit, and check if any scheduled tasks are disabling Defender.

Should I use a third-party antivirus if Defender is broken?

You can, but it’s better to fix Defender first. Third-party antivirus can conflict with Defender if not fully removed, and you’ll end up with two security tools fighting each other. If you need immediate protection, install a reputable antivirus, but then still fix Defender and uninstall the third-party tool afterward.

Related

• Add a Keyboard Language on Windows, Mac & Mobile
• How to Capture Stop Motion Videos on Android
• Tar Command in Linux: How It Works