Windows App Paths

Some people might know about this already, but it's a cool detail of Windows that I found fascinating. Pretty much everybody knows you can type program file names into the Run dialog and have them appear, and you can add directories to the PATH environment variable to make the Run dialog search those places if you don't supply a path.

But, some applications can launch even if their executable is not on the PATH. This is through a feature called App Paths. It is a registry key that maps executable file names (non-qualified) to full paths and provides their initial directory.

There are two instances of it, one under HKLM and another under HKCU, for everyone and the current user, respectively. You can find it at HK??\Software\Microsoft\Windows\CurrentVersion\AppPaths. Each subkey is the name of a program you can type at the Run dialog.

The default value of each key is the full path to the executable. (It doesn't even have to have the same file name as the unqualified name!) The Path value provides the initial directory. There seem to be some other properties that can be set, like UseURL and BlockOnTSNonInstallMode, but I'm not entirely sure what they do.