microsoft-windows-bits-client-dl.man

Windows instrumentation manifest Reference

A .man file on Windows contains an instrumentation manifest in XML. The manifest defines event providers and event channels for the Windows event system, and performance counters use the same format. Tools such as wevtutil register the manifest with the system. System components ship .man files together with their binaries. On Unix systems, the same extension identifies manual pages for the man command.

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.