Dear community, I am desperately looking for a way to handle custom protocols in Firefox on macOS (both up-to-date). I have seen many questions and many answers, most of them are outdated or irrelevant. On our intranet, some of the pages have links pointing to "ictfast:xxxxxx". The first part (ictfast) is never changing. The second part (xxxxxx) can be anything. I would like to run an external application when people click on such links. What I have done so far: step #A1: In "about:config", I created and set the key "network.protocol-handler.expose.ictfast" to false. step #A2: I clicked on a link "ictfast:xxxxxx" step #A3: A box appeared letting me choose my external application After these steps, if I click on a "ictfast" link, the application runs but I can't access the content in "xxxxxx". To reproduce this, it is very simple: step #B1: open Automator step #B2: create a new Application step #B3: add the "Run Shell Script" actions step #B4: choose "Pass input" to as arguments" step #B5: remove the default content of the shell script step #B6: type in `echo "$@" > /tmp/args.txt` (without the backticks) step #B7: save and choose this app in step #A3 Now if you click on a "ictfast" link, the file in "/tmp/args.txt" is created, but is empty. There is no arguments passed to the applications. I was naively believing that when clicking on a "ictfast" link, Firefox would internally run the command `/foo/bar/whatever.app "address"`. But it seems to be more complicated and cryptic than that. Could anyone help me on this? Thanks!