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I've searched high and low for the answer to this but no luck. This may appear at first glance to be a simple request but what I actually want seems to be a bit tricky.

I am running multiple instances of Firefox on my Mac OS X Lion machine (using the shell script at to do so). It works great, BUT the new instance automatically loads everything that is open in the current (first) instance. I'd like to know if there is some modifier that can be applied, that would override this behavior ONLY for this launch of FireFox. A single-use suppression, if you will.

To be clear, Safe Mode will not do, I do not want to disable this behavior in preferences, and I'm not looking for something where I would have to launch FireFox, make a tweak, then restart again. I need a way to disable this behavior at any arbitrary moment when I decide to launch FireFox.

Anyone got any clever ideas?

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Well damn, just writing out the question made me realize an easy answer. I merely commented out one line (the cp line) from the shell script, and now a new instance launches without anything from the previous profile. Problem remains that I would like all my previous profile's adons, just not the tabs. Anyone? – Jonathan van Clute Jul 2 '12 at 6:01
OK, I believe I have a final solution. Created a second "fresh" profile, copied my Extensions folder over from the old one to the new. Then when the new instance of FF launched, it prompted me to reinstall all those addons. I let them all install, restarted, and now I can launch a new "fresh" FF instance any time. Initial directions found here: – Jonathan van Clute Jul 2 '12 at 6:30

You could also install the Session Manager addon, then setting your start page to about:startpage in Firefox. Now you would be asked on each start whether to restore which tabs (you can select all, no, one, a few...) or start with a fresh session. Session Manager also creates backups of your sessions, so you could return to a previously saved in case of need -- or store useful "session profiles" (i.e. combination of open tabs) for later use.

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That's also a handy suggestion, thanks for sharing! – Jonathan van Clute Jul 2 '12 at 7:41
Exactly what I needed! Thanks! – ChocoDeveloper Feb 12 '13 at 6:42

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