How to Repair the “Virus Definitions Update Failed” Issue on Avast Antivirus

  • Avast Antivirus is Avast’s Internet security software for Microsoft Windows, macOS, Android, and iOS.
  • The reason why you cannot update Avast virus definitions is that the recent update was installed on an abnormal date.
  • Even if the update is properly installed on your computer, the virus definition will generate an error.
  • The solution to the “Virus definition update failure” problem is to update your Avast to the latest version of Avast.

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Although Avast Antivirus is a great program for protecting your device, it may sometimes experience a technical malfunction. One of the more common technical glitches with Avast Antivirus is a failed virus definition update. Here is the complete literature on how to fix the “Virus Definitions Update Failed” issue on Avast Antivirus if you have encountered the same issue.

Even on a clean install, AVAST FREE cannot be updated and reinstalled (!!! ).

In the event that you try updating virus definitions and receive the “Virus Definition Failed” error, but the error persists after you’ve tried everything? Here is the solution to “Virus Definition Failed” in Avast Antivirus, which we’ve discussed in this blog.

Avast Antivirus Update

Your antivirus protection must be updated regularly by downloading and installing the latest virus definitions database (VPS). Avast Business Antivirus provides a shell script that performs this task for you.

Avast Antivirus protects your computer, browser, and phone from malware and viruses for Windows, macOS, Android, and iOS operating systems. It provides free and premium versions for Windows, macOS, Android, and iOS devices.

What is the reason for the “Virus definitions update failure” problem in Avast Antivirus?

  • The reason why you cannot update Avast virus definitions is that the recent update was installed on an abnormal date. Therefore, even if the update is properly installed on your computer, the virus definition will generate an error.
  • When Avast fails to update or is canceled during the installation process, this error can occur.
  • Incompatibility with your existing version of Windows may also lead to Avast virus definitions not being updated, as your Windows may not be updated regularly.

The solution to the “Virus definition update failure” problem in Avast Antivirus

Updated: December 2023

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Update your Avast to the latest version

Check for expected updates, install them, and update Avast as well. The easiest way to fix your Avast problem is to fix the incompatibility issues.

  1. You can find the menu and settings in Avast by starting it.
  2. The CHECK FOR UPDATES button is located on the ‘update interface’.
  3. If the problem persists after the update, try rebooting the system.

Your Avast installation files will need to be restored if no updates are expected.

  1. To view Programs and Features, open the Windows Control Panel (see large icons).
  2. Choose Edit from the application’s menu.
  3. Restore the client software by clicking Restore in the new window and waiting for Avast to modify the data files.

Reinstalling Avast

It may require you to use a professional uninstaller. Or you may need to boot up your computer in safe mode and uninstall Avast in that mode. If Avast still does not update the virus definitions after trying the above method, try reinstalling Avast.

  1. Click OK to open the Run window and type MSConfig.
  2. The Safe Boot option can be found on the Boot tab, and it can be enabled by turning it on.
  3. Safe mode can be entered by restarting your computer.
  4. Remove any remaining files from your computer with avastclear.exe.
  5. Using the official website, install the latest version of Avast after rebooting your PC in normal mode.
  6. Avast won’t update virus definitions if these corrupted files are removed.

Utilize the built-in troubleshooting menu

  1. You can access the settings by opening Avast and going to the menu.
  2. The Troubleshooting window will appear; click on CALL REPAIR on the bottom of the screen.
  3. Restore will begin after you click Yes.

RECOMMENATION: Click here for help with Windows errors.

Frequently Asked Questions

  1. Start Avast Antivirus and click on the menu icon.
  2. Select Settings.
  3. In the Settings menu, click the General tab.
  4. Select the Update sub-tab.
  5. Click the Check for updates button.
  6. If an update is pending, click the available option to download and install the update.

This problem was caused by some bugs in Avast software that were fixed in Avast version 6.16. This problem was fixed in the latest Avast updates, so you need to install an updated version of Avast software to solve it.

If Avast Antivirus does not update, you need to update it regularly for it to work effectively. Sometimes an unknown error may occur during an Avast update. Incorrect DNS settings or a firewall running on your system can cause these errors.

Right-click on the Avast icon in the notification area of the Windows taskbar and select Update > Virus engine and definitions. If your Avast antivirus does not check for updates automatically, click Check for updates. Wait for Avast scanner to check and install virus definition updates.

Updating Antivirus Definitions

Update utilities are not always included with antivirus programs. You can get new virus definitions from the developer’s website if you’re using such software. If you’re using such software, please note that some developers need to know your version number before you can get updates. Some popular antivirus programs are listed below with links to their web pages.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog,, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.