Blog

How to Fix Windows Defender Error 0x8000404 on Windows 11: Step-by-Step Solutions

Windows Defender is an essential security tool built into Windows 11 to protect your computer from malware and other threats. Sometimes, users encounter error codes that disrupt its normal functioning. One such error is 0x8000404, which can prevent Windows Defender from updating or running properly.

This article will guide you through simple, step-by-step solutions to fix the Windows Defender error 0x8000404. Each method is explained clearly, so even beginners can follow along without confusion.

By following these instructions, you can restore your Windows Defender and keep your system secure. Let’s start with some quick checks before diving into troubleshooting.

Remember, taking your time and carefully completing each step will help resolve the issue efficiently.

Quick Note: Prerequisites and Initial Checks

Before attempting any fixes, ensure the following:

  • Your Windows 11 system is connected to the internet. Updates require an active connection.
  • Your system date and time are set correctly. Incorrect settings can cause update errors.
  • No other antivirus software is interfering with Windows Defender. Conflicts can cause error 0x8000404.
  • You have administrator rights on your computer. Some fixes need elevated permissions.

Step 1: Restart Your Computer

Sometimes, a simple restart can clear temporary glitches causing the error. Restarting refreshes system processes and can solve minor bugs.

  1. Click the Start button in the bottom-left corner.
  2. Select the Power icon.
  3. Choose Restart from the options.
  4. After your PC restarts, check if Windows Defender is working normally.

Step 2: Run the Windows Defender Troubleshooter

Windows 11 includes a built-in troubleshooter for security issues, which can automatically detect and fix problems with Windows Defender.

  1. Open the Settings app by pressing Win + I.
  2. Go to System > Troubleshoot.
  3. Select Other troubleshooters.
  4. Find Windows Security in the list and click Run.
  5. Follow the on-screen instructions and allow the troubleshooter to complete.
  6. Restart your computer and check if the error persists.

Step 3: Update Windows 11

Sometimes, Windows Defender errors occur because your system or security definitions are outdated. Installing the latest Windows updates can fix bugs and improve Defender’s functionality.

  1. Press Win + I to open Settings.
  2. Click Windows Update in the left pane.
  3. Select Check for updates.
  4. Download and install any available updates.
  5. Restart your PC after the updates install.

Step 4: Check and Restart Windows Defender Services

Windows Defender relies on certain system services to run smoothly. If these services are stopped or malfunctioning, errors like 0x8000404 can appear.

  1. Press Win + R to open the Run dialog box.
  2. Type services.msc and press Enter.
  3. In the Services window, scroll down and find Windows Defender Antivirus Service.
  4. Right-click it and select Restart. If the service is stopped, choose Start.
  5. Also, check Windows Defender Firewall and restart/start it if needed.
  6. Close the Services window and test Windows Defender again.

Step 5: Run System File Checker (SFC) and DISM Tools

Corrupted system files can cause Windows Defender errors. The System File Checker (SFC) and Deployment Image Servicing and Management (DISM) tools scan and repair these files.

  1. Click the Start button, type cmd, then right-click Command Prompt and select Run as administrator.
  2. In the Command Prompt window, type the following command and press Enter:
sfc /scannow

This process may take some time. When it finishes, type the following commands one by one, pressing Enter after each:

DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth

After these finish, restart your computer and check if Windows Defender is working.

Step 6: Reset Windows Security App

If the Windows Security app itself is corrupt, resetting it can fix the error without affecting your files.

  1. Open Settings (Win + I).
  2. Go to Apps > Installed apps.
  3. Find Windows Security in the list and click the three dots next to it.
  4. Select Advanced options.
  5. Scroll down and click Reset. Confirm if prompted.
  6. After reset, open Windows Security and see if the error is resolved.

Alternative Method: Use PowerShell to Re-register Windows Defender

If previous steps don’t work, you can try re-registering Windows Defender using PowerShell. This method refreshes Defender’s app registration in Windows.

  1. Press Win + X and select Windows Terminal (Admin).
  2. In the terminal, paste the following command and press Enter:
Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)AppXManifest.xml"}

Wait until the process completes, then restart your PC.

Frequently Asked Questions (FAQs)

What causes Windows Defender error 0x8000404?

This error often occurs due to corrupted system files, outdated Windows updates, conflicts with other antivirus programs, or issues with Windows Defender services.

Is it safe to disable Windows Defender to fix this error?

Disabling Windows Defender is not recommended as it leaves your system vulnerable to threats. Instead, follow the troubleshooting steps to fix the error.

Can a third-party antivirus cause this error?

Yes, some third-party antivirus software may conflict with Windows Defender, causing errors. Consider temporarily disabling or uninstalling other antivirus programs to check if the error resolves.

Do I need to back up my files before trying these fixes?

Most of these steps are safe and do not affect personal files. However, it’s always good practice to back up important data regularly.

Where can I find official help if these steps don’t work?

You can visit the Microsoft Support website or contact Microsoft customer service for professional assistance.

When Nothing Works

If you have tried all the above solutions and still face error 0x8000404, consider the following final options:

  • Perform a System Restore: Restore your PC to a point before the error appeared. This can undo recent changes causing the issue.
  • Reset Windows 11: You can reset your operating system without losing personal files by going to Settings > System > Recovery > Reset this PC.
  • Contact Microsoft Support: For persistent problems, getting expert help ensures a safe and proper fix.

Always ensure you have backups before performing system restores or resets.

Conclusion

Windows Defender error 0x8000404 can be frustrating but is usually fixable with simple steps. Starting from restarting your PC to running system scans and resetting the security app covers most causes of the issue.

Keeping Windows updated and ensuring no conflicting software is installed plays a big role in preventing such errors. If problems persist, advanced methods like PowerShell re-registration or system restore can help.

Following this guide will help you restore Windows Defender’s functionality and keep your Windows 11 computer protected against threats.

Leave a Reply