I found a couple of things to try if you want Firefox to *always* open or re-open in fullscreen (kiosk-style) mode <—- this is not the same as maximized, btw, just for anyone who wasn’t sure.

Option 1:

There’s this addon:


Option 2:

Another addon, along with code that goes in the chrome folder in your user profile.


^^ After that addon is installed, close the browser and put the following lines into a file called “userChrome.js”. <-you may have to create it. Do it the way you would a new text file, only give it the .js extension.

/* Firefox userChrome.js */

if (location == “chrome://browser/content/browser.xul”) {
setTimeout(function() {
if (window.opener == null) {
Services.prefs.setBoolPref(“browser.fullscreen.autohide”, true);
window.fullScreen = true;
}, 2000);

I know I know— F11. But that gets old. I’d rather do it in one of the above ways, then forget about it. I *hope* I can forget about it.

ETA: This is the thread that got me on my way.