VSTO File Extension

Have a problem opening a .VSTO file? We collect information about file formats and can explain what VSTO files are. Additionally we recommend software suitable for opening or converting such files.

What is the .VSTO file type?

Denoting the VSTO Add-in (.vsto) file type, the .vsto filename extension relates to the Visual Studio Tools for Office (VSTO). VSTO serves as an interoperability bridge between Microsoft's .NET technology and the Common Language Runtime (CLR) environment in Microsoft Office that allows to write and deploy .NET-based Office customizations.

The .vsto file itself is an XML control file of a Microsoft Office customization add-in. It binds together the add-in's DLL and other files and defines its behavior. VSTO add-ins are usually packaged as MSI-based installer executables, to be run on the user's side.

For a VSTO add-in to install correctly, the .vsto file type must be associated with the VSTO Execution Engine (VSTOEE), and a proper version of Microsoft Office with the VSTO runtime must be present. When installed, a VSTO add-in is expected to be loaded automatically during startup of its host application, provided that proper registry entries have been set up during installation, and the add-in is enabled in the application's settings (e.g., "COM Add-Ins" in Microsoft Excel).

Software to open or convert VSTO files

You can open VSTO files with the following programs: 

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