The .NET Framework 4.5.1 is available on Windows Update and WSUS

The .NET Fundamentals Team

Update (2017): See .NET Framework Releases to learn about newer releases. This release is unsupported.

We are happy to announce that the .NET Framework 4.5.1 and its language packs are now available via Windows Update (WU) and WSUS. You can learn more about the release from the What’s new in the .NET Framework 4.5.1 topic.

This update is available in the Windows Update applet within the Control Panel. You may need to use the Check for updates feature from within the Windows Update applet to get the release to show up.

Automatic Updates

The .NET Framework 4.5.1 release is being made available as a Recommended Update, this means that users with Automatic Updates configured to install automatically will get the release automatically. This is the default experience. Users that have modified their AU settings to notify them when updates are available or downloaded will see a notification in their system tray about this update.

We have throttled the distribution of the release via Automatic Updates, which means that a subset of users will be updated each day instead of all users getting the update on the first day. This is done so we can receive and react to customer feedback regarding this update. So if you don’t get the update offered on the first day and do not want to wait until the update is offered you can use the Check for updates feature, which is not throttled, as described above.

Windows Server Update Services (WSUS) and Catalog

WSUS administrators should see this update in their WSUS admin console. The update is also available in the MU catalog for download and deployment.

Blocking the automatic deployment of .NET Framework 4.5.1

In some cases enterprises may have client machines that connect directly to the public Windows Update servers rather than to an internal WSUS server. In such cases, an administrator may have a need to prevent the .NET Framework 4.5.1 from being deployed to these client machines, for example in order to allow testing of internal/LOB apps to complete.

Admins can deploy a registry key to machines in order to prevent the .NET Framework 4.5.1 from being offered to those machines. More information about how to use this blocker registry key can be found in the following Microsoft Knowledge Base article:

KB2721187  How to temporarily block the installation of the .NET Framework 4.5.1 and its corresponding language packs. 

Supported Operating Systems for the release

The .NET Framework 4.5.1 is being offered via Windows Update and WSUS to computers running the following operating systems:

  • Windows Vista SP2, Windows 7 SP1, Windows Server 2008 SP2, Windows Server 2008 R2 SP1, Windows Server 2012

On Windows 8 and Windows RT customers can get the .NET Framework 4.5.1 by upgrading their computer to Windows 8.1 and Windows RT 8.1 respectively. There is no Windows Update offering of the .NET Framework 4.5.1 for these platforms.

Lastly, the following operating systems ship with the .NET Framework 4.5.1 already available in-box, so you do not need to deploy or install the update, you already have the latest bits.

  • Windows 8.1, Windows RT 8.1 and Windows Server 2012 R2

Developing using .NET Framework 4.5.1 and Visual Studio 2012

Developers using Visual Studio 2012 can build applications targeting the .NET Framework 4.5.1 by installing the .NET 4.5.1 Developer Pack. The developer pack is a single package containing both the .NET Framework 4.5.1 runtime as well as the .NET Framework 4.5.1 Multi-Targeting Pack which exposes the updated API surface for developers.  You can download the .NET Framework 4.5.1 Developer Pack from here:

Known Issues

We have documented known issues that we’re currently aware of in the Knowledge Base Article 2890857 along with possible workarounds and/or mitigations. This list will be updated with other issues as we become aware of these in the future.


Finally, if you have feedback to share about this release you can send an email to:



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