Download the latest free virus definition files and update Defender antivirus

Windows Defender Definitions (64-bit)

Windows Defender Definitions (64-bit)

  -  144 MB  -  Freeware
  • Latest Version

    Windows Defender Definitions (64-bit) LATEST

  • Review by

    Michael Reynolds

  • Operating System

    Windows 8 (64-bit) / Windows 10 (64-bit) / Windows 11

  • User Rating

    Click to vote
  • Author / Product

    Microsoft Corporation / External Link

  • Filename


Microsoft Windows Defender Definition Updates 64bit is a crucial security addon that enables the core antivirus service running on all modern versions of Windows OS to get access to the latest antivirus definition and gain the ability to detect, quarantine, and erase a wide array of software threats on desktop and laptop PCs.

While the built-in Windows Defender relies heavily on the Microsoft Windows Update service to deliver the latest add-ons, upgrades, and definition archives, many Windows users do not have PCs that are connected to the internet. But such machines are not safe from malicious software threats which can affect them any time such PCs come in content with external storage mediums such as CDs, DVDs, and flash storage drives.

If the local antivirus software is not keeping up with the ever-evolving security solutions, it can fail to detect an untold amount of malware applications that can cause a wide array of issues, including lost files, ransoming of complete local storage content (ransomware), crashes, loss of app stability, spying, and data collection, loss of hardware performance, destruction of hardware, OS crashing, inability to boot OS or even total loss of hard drive data.

Microsoft Defender Definition Updates can prepare modern Windows OS releases (ranging from Windows 7 to Windows 10 and Windows 11) to instantly detect any malicious file. Users are recommended to always keep their Definition add-ons current, even if that means regular downloading and installing update files manually.

For PCs that are connected to the internet, this procedure is done automatically by background Windows services, but users are recommended to check from time to time if the updates have arrived. If the PC is having issues automatically retrieving the latest malware definition updates, then manual downloading of Windows Defender Definition Updates files is needed.

To download and install a Microsoft Windows Defender update, you can follow these steps:

Open Windows Security: You can access Windows Security by clicking on the Start button, selecting "Settings," and then clicking on "Update & Security." From there, choose "Windows Security" in the left sidebar.

Check for updates: In the Windows Security window, click on "Virus & threat protection." Under the Virus & threat protection settings, select "Check for updates." Windows Defender will now check for available updates.

Download and install updates: If any updates are found, Windows Defender will automatically download and install them. This process may take some time depending on the size of the update and your internet connection speed. Make sure to keep your computer connected to the internet during this process.

Restart if necessary: After the updates are installed, you may be prompted to restart your computer. If so, save any open files and close applications before proceeding with the restart.

Verify updates: Once your computer restarts, open Windows Security again and navigate to the "Virus & threat protection" section. Click on "Check for updates" to confirm that all the updates have been successfully installed. If no further updates are found, you are up to date.

Automated Updates

Ensure that your antimalware solution stays up to date with the latest threats by enabling automatic updates through Windows Update. If you encounter any issues with Windows Update, utilize the troubleshooter. If you haven't already, activate Microsoft Defender Antivirus to benefit from automatic updates.

Manual Update Activation

By manually triggering an update, you can promptly download and apply the most recent security intelligence, which may also resolve problems related to automatic updates. Microsoft Defender Antivirus and other Microsoft antimalware solutions offer the option to initiate a manual update.

For Windows 11/10, access the Windows Security Virus & Threat Protection screen and select "Check for updates" to ensure you have the latest updates.

Enterprise administrators can also push updates to devices within their network. To trigger an update and clear the current cache, execute the following commands as an administrator using a batch script:
  • cd %ProgramFiles%\Windows Defender
  • MpCmdRun.exe -removedefinitions -dynamicsignatures
  • MpCmdRun.exe -SignatureUpdate
Windows Defender Definitions 64-bit is distributed in 32-bit and 64-bit forms, and users must correctly pick which version of the file they can install on their PC. The entire procedure of getting this security addon installed on the PC is automated and lasts just a few seconds.

Also Available: Windows Defender Definitions (32-bit)