How to fix
Windows Defender Definition Update Error Code 0x80072af9
on Windows

When I check for updates in Windows Defender, I receive an error message, which declares that the definition updates cannot be checked or installed. The error code is 0x80072af9. What should I do?

Windows Defender is a signature-based anti-virus owned by Microsoft, which comes by default with Windows 10 operating system. While it was first used as a free antispyware tool for Windows XP, 7, and Vista, it has been improved significantly and made into a full anti-virus program built into Windows 8 and 10. AV-TEST revealed that Windows Defender is capable of recognizing and eliminating 94.5% of PC threats, meaning that it's sufficient to protect the system from both minor and severe computer threats. However, if Windows Defender lacks for the latest definitions, it may fail in detecting the newest cyber threats. Therefore, running definition updates on a regular basis is very important to prevent security breaches. The problem is that sometimes Windows Defender definition updates fail to download due to various reasons. One of the current Windows Defender definition update errors is 0x80072af9. Usually, it shows up immediately when a PC’s owner opens Windows Defender or attempts to check for updates. The error won’t let to install the latest definition update, what means that your operating system may have some security breaches. To fix Windows Defender error code 0x80072af9, you should try the following methods.

How to Fix Windows Defender Definition Update Error Code 0x80072af9?

Method 1. Disable third party anti-virus or remove its leftovers

Some Windows experts claim that the culprit of the Error Code 0x80072af9 may be the Norton or McAfee applications or their file leftovers. Therefore, make sure to disable any third-party anti-virus (or even remove it). If you have run any of these tools before, but they are long gone from your PC, it’s advisable to perform a full scan with [d1] and make sure that all file leftovers have been removed successfully. It has been noticed that McAfee and Norton tools are quite notorious for not uninstalling cleanly, which is why Windows Defender may be colliding with their remnants. This tool additionally checks the system for malware, delete corrupted files, remove other junk files, and ensure the full system’s optimization.

Method 2.  Install all available Windows Updates

Microsoft developers are aware of most of the Windows 10 bugs and are working hard to release fixes ASAP. To get support and keep the system working smoothly, it’s vital to install Windows Updates regularly. Therefore, to fix the 0x80072af9 bug, it’s advisable to run Windows Updates:

• Press Windows key + I and select Update & Security.
• Click Check for Updates and wait until the system performs a scan.
• If you have some updates available, install them and check if Windows Defender definition update error 0x80072af9 vanished. If not, move on to the next fix.

Method 3. Update Windows Defender from within its interface

• Right-click on an empty space on the desktop and select New -> Shortcut.
• Create a shortcut for %SystemRoot%\System32\Cmd.exe /c Cleanmgr /sageset:35 & Cleanmgr /sagerun:35 command.
• Right-click the shortcut and run it as an administrator.
• The press Windows key + X and select Command Prompt (Admin).
• If a UAC shows up, click OK to proceed.
• Type Dism /Online /Cleanup-Image /StartComponentCleanup command and hit Enter.
• Once done, try to install Windows Defender definition update.

Please let us know if these methods helped you to fix Definition Update Error Code 0x80072af9 successfully.