Installing the .NET Framework 4.5

This topic provides links for installing the .NET Framework 4.5 on Windows 7, Windows Server 2008 SP2, and earlier versions of the Windows operating system. In addition, it provides links for installing the .NET Framework 4.5.1 Preview on Windows 8, Windows Server 2012, and earlier versions of the Windows operating system. Windows 8.1 Preview and Windows Server 2012 R2 Preview include the .NET Framework 4.5.1 Preview, and Windows 8 and Windows Server 2012 include the .NET Framework 4.5, so you do not have to install the .NET Framework separately on those operating systems.

For a full list of supported operating systems and hardware requirements, see .NET Framework System Requirements. For a general introduction to the .NET Framework for both users and developers, see Getting Started. To read about the architecture and key features of the .NET Framework, see the overview.

You can download the .NET Framework directly through the links in this article or through these Microsoft Download Center pages:

• NET Framework 4.5.1 Preview

• NET Framework 4.5

Important notes:

• The .NET Framework 4.5 redistributable was updated on October 9, 2012 to correct an issue related to an improper timestamp on a digital certificate, which caused the digital signature on files produced and signed by Microsoft to expire prematurely. If you previously installed the .NET Framework 4.5 redistributable package dated August 16, 2012, we recommend that you update your copy with the latest redistributable from the Microsoft Download Center. For more information about this issue, see Microsoft Security Advisory 2749655 and Knowledge Base article 2770445.

• The .NET Framework 4.5.1 Preview is an in-place update to the .NET Framework 4.5.

• The .NET Framework 4.5 and .NET Framework 4.5.1 Preview replace the .NET Framework 4. When you install these versions on a system that has the .NET Framework 4 installed, the assemblies are replaced.

• Uninstalling the .NET Framework 4.5 also removes pre-existing .NET Framework 4 files. If you want to go back to the .NET Framework 4, you must reinstall it and any updates to it. (See Installing the .NET Framework 4.)

• You must have administrative credentials to install the .NET Framework 4.5 and its point releases.

The redistributable packages for the .NET Framework 4.5 and the .NET Framework 4.5.1 Preview provide the assemblies for an app or control that is built to target those versions. These files must be installed on each computer where the app or control runs. Two types of redistributable packages are available:

• Web bootstrapper (web installer), which downloads the required components and appropriate language pack from the web.

• Stand-alone redistributable (stand-alone installer), which contains the required components for deployment, but does not contain language packs. Use this installer if you cannot rely on having a consistent Internet connection.