Explorer - options for files without extensions

I've not seen this discussed before. As well as setting options for specific file types, you can do this for files with no extension. I haven't found any reference to this in Microsoft documentation, but Raymond Chen mentioned this in 2007. What is the difference between the Folder and Directory (and other special) progids? - The Old New Thing

It seems to work perfectly well in Windows 11. You shouldn't see many files like this, most examples I have come from source code downloads, such as makefiles or documentation.


My interest is simply to read the file using the built-in text preview function in explorer. Setting the PerceivedType to text gets you this, as it does for any file type that doesn’t have a hard coded PerceivedType. Obviously you can set up normal file associations if you want.

I think the problem is Windows doesn't have the equivalent of /etc/magic for guessing at file types, when there is no file extension.

Skeptic Mike said:

I've not seen this discussed before. As well as setting options for specific file types, you can do this for files with no extension. I haven't found any reference to this in Microsoft documentation, but Raymond Chen mentioned this in 2007. What is the difference between the Folder and Directory (and other special) progids? - The Old New Thing

It seems to work perfectly well in Windows 11. You shouldn't see many files like this, most examples I have come from source code downloads, such as makefiles or documentation.

My interest is simply to read the file using the built-in text preview function in explorer. Setting the PerceivedType to text gets you this, as it does for any file type that doesn’t have a hard coded PerceivedType. Obviously you can set up normal file associations if you want.

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Thanks, very useful for the hosts file.