How to manually download the latest definition updates for Windows Defender

This article describes how to manually download the latest definition updates for Microsoft Windows Defender.

To manually download the Windows Defender definitions for your computer, follow the steps for your operating system type, 32-bit version or 64-bit version.

32-bit versions of Windows

To download the Windows Defender definition update file for 32-bit (x86-based) versions of Windows, click the following link: After you click this link, click Run to install the definition file immediately, or click Save to save the definition file to the computer. If you click Save, remember the folder where you save the file.

To install the saved definition update file, click Start, click Run, locate the folder where you saved the definition file, double-click the Mpas-fe.exe file, and then click OK.

Note To install the file on a Windows Vista-based computer, right-click the file, and then click Run As Administrator to install it.

When the definition file runs, a file extraction dialog box appears. The dialog box indicates that the definition update is installing. After the file extraction dialog box closes, you can verify that the Windows Defender definitions have been updated. To do this, open Windows Defender, and then check the definition version that is listed in the box at the bottom of the Windows Defender Home dialog box.

Corporate customers should use Windows Server Update Services (WSUS) version 2.0 or later versions to distribute Windows Defender definition updates. However, these customers can also use a user logon script to manually install a definition update by running a Windows Defender definition update file.

The Windows Defender definition update file (Mpas-fe.exe) can use the -q command-line execution switch. This switch installs the definition update in quiet mode. Quiet mode suppresses the definition file extraction dialog box. For example, type the following command:

64-bit versions of Windows

If you run a 64-bit version of Windows, download the Windows Defender Update Definition file by clicking one of the following links.

Note You must be running a 64-bit version of Windows to run a 64-bit version of Windows Defender. 64-bit versions of Windows include x64-based versions and Itanium-based versions.

To download the Windows Defender definition update file for x64-based versions of Windows, click the following link:

To download the Windows Defender definition update file for Itanium-based versions of Windows, click the following link:

Technical support for x64-based versions of Microsoft Windows

If your hardware came with a Microsoft Windows x64 edition already installed, your hardware manufacturer provides technical support and assistance for the Windows x64 edition. In this case, your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation by using unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with a Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware. If you purchased a Windows x64 edition such as a Microsoft Windows Server 2003 x64 edition separately, contact Microsoft for technical support.

For product information about Windows XP Professional x64 Edition, visit the following Microsoft Web site: For product information about x64-based versions of Microsoft Windows Server 2003, visit the following Microsoft Web site: