How does start find applications that are not in %PATH%?

Question

Firefox is not in my %PATH%, so

c:\> where firefox

tells me, that firefox isn't found, nor does

c:\> firefox

start the browswer.

However, if I type

c:\>start firefox

Windows (or cmd.exe) is able to locate the executable. How is this?

Answer 1

The start command does not rely only on the information in %PATH%. In particular, it also looks for a registry key which lists known applications, namely HKCU\Software\Microsoft\Windows\CurrentVersion\App Paths\ as well as HKLM\Software\Microsoft\Windows\CurrentVersion\App Paths\.