How to run multiple independent Firefox sessions simultaneously

TL;DR: firefox -no-remote -P

For years (way over a decade, actually), I’ve used multiple browsers at the same time. What used to be a workaround to sites working better in some particular browser then became a very convenient way to keep several different sessions opened simultaneously (with 2 very separate “cookie world” and stuff). That’s useful for instance to be connected to 2 different mailboxes from the same provider, or to use different proxies simultaneously (one per browser).

But the browser world moves fast, and now it seems my favorite Firefox forks (Chrome support for SOCKS proxies is worthless so that’s not an option) are all vanishing: Pale Moon has been lagging behind for a long time, and now Cyberfox is being discontinued. Waterfox is still here, but they’re not really a fork, and they are so close to vanilla Firefox that they actually share its profiles and session (if you try to run Waterfox while Firefox is running, or the other way around, it will tell you Firefox is already running). So, it’s becoming hard to find distinct browsers.

In my despair, I tweeted to Waterfox about that problem of not being able to multi-session, and they pointed me to the -no-remote flag. I already used several Firefox profiles, but so far I was only able to run a single one at a time. What that flag does is that it basically allows to run several profiles at the same time (to use it, edit your Firefox shortcut and add it at the end of the command line). I guess I should have searched harder.
Problem solved already, then 🙂 But now, every time you run Firefox the profile manager will pop up. If you want to skip this, you can create separate links for each of your profiles, by adding also -P “profile_name” in the command line. Or even -profile “profile_path”, if you like moving stuff around 😉 All those options are detailed in the link I gave previously.

Last but not least, a little advice to avoid mixing up your sessions: set them up each with a different theme ^^