windowsclient.mshc

Microsoft Help container Reference

A .mshc file is a help content container for the Microsoft Help Viewer. The file is a ZIP archive with HTML topic pages and assets. Documentation for Visual Studio and other Microsoft products ships in this format. The Help Library Manager installs the container into the local help store. The related .mshi file carries the index data.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.