How Does Google Chrome Launch Desktop Apps?

i don't really know the terminology so im going to start with an example. If I click a magnet link, Google chrome asks if i want to launch a torrent client. I click ok and chrome

Solution 1:

It depends exactly on the OS, but in general, another desktop program can register a specific protocol, or URI scheme, to open up a program. Then, when Chrome doesn't know how to deal with a protocol, it'll just hand it over to the OS to deal with.

In Windows for example, they're configured by putting something into the system registry under a specific key (https://msdn.microsoft.com/en-us/library/aa767914(v=vs.85).aspx).

Most applications will setup themselves as a default for the particular protocol when installed.

Solution 2:

Chrome is a "desktop" program. It can open any program exposed from the operating system.

A link can contain a specific protocol instead of http://, the OS can have a map that ties protocols directly to installed programs. Chrome is not communicating with the app at any point. It only tells the os to open a resource at a given url with a given program.