How do I install a VSIX file in Visual Studio?

VSIX is a Visual Studio extension installer. You must have Visual Studio 2010 or newer in order to install them, but you should be able to install it by double-clicking the .vsix file. Alternatively you should be able to install it from within the VS Extension Manager (Tools->Extension Manger)

See more about VSIX files at Quan To's Visual Studio Extensibility blog

The above answers didn't help me; I couldn't install it through the extension manager and there was not default application for .vsix. However, I needed to open it (right click > Open with...) with Microsoft Visual Studio Version Selector and it worked.

Small update: For VS 2013, you need the corresponding version of NuGet: http://visualstudiogallery.msdn.microsoft.com/4ec1526c-4a8c-4a84-b702-b21a8f5293ca. Otherwise, the version selecter will tell you it's already installed on all fitting versions.

How to install Visual Studio Extensions

To summarise, there are three options:

1. Install via Extension Manager (Tools/Options)
2. Install via Visual Studio Gallery.com (download and open directly or save then double-click)
3. Install via "xcopy" into %localappdata%\Microsoft\VisualStudio\10.0\Extensions

If all the above options fail, try installing it from the VS Developer command-line. Here's how (on StackOverflow):

How to install Visual Studio Gallery extensions from command line

VSIXInstaller.exe /quiet some_extension.vsix

You can find VSIXInstaller here (on your local PC - depending on the Visual Studio version replace 14.0 by the version you're using):

C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE

To display the installer dialog(s), remove the /quiet option.

Note:

• To uninstall a VSIX extension, you need to know its vsixID (here is described how to get it), then you can use

  VSIXInstaller.exe /uninstall:vsixID

• To install/uninstall VSIX files for a specific Visual Studio version, use the switches /skuName:name and /skuVersion:version; you can see all options of the command line tool if you type VSIXInstaller.exe /? in the developer command prompt.