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Using the Firefox profile manager for sanity

My Firefox is a mess

I use Firefox in three main ways : "normal" browsing, web development and security stuff. These activities have different requirements :

When browsing normally, I want to see as little ads as possible and be tracked as little as possible while having quick access to my bookmarks. I also use some convenience extensions.

When I'm developing a web app, I want to avoid the situation where one of my regular extensions is somehow breaking the site, and quick access to another set of convenience extensions (things like react-devtools ).

Finally, when I'm working on a web security thing, I want to see the original pages' content (including ads), my traffic to go through Burp's Proxy and quick access to a third set of extensions ( Shodan.io, builtwith, etc.).

Those requirements are somewhat incompatible, and trying to set up Firefox for all of this at once ends up creating a cluttered mess of an UI that requires a billion manual actions to do something as simple as looking at adcodes.

The profile manager

If that sounds familiar, you may or may not know Firefox comes with a solution : the https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles.

A firefox profile has its own set of settings, extensions and bookmarks; and the profile manager allows you to, well, manage them. Once you have created a second profile, the browser will prompt you for which one to use when starting. It is also possible to use several profiles at the same time in different windows.

It's a somewhat hidden feature, and discovering it has chaned my life for the better so I highly recommend using it to anyone having the same problem as I had.

How to use it

As I mentioned, the profile manager will be displayed every time you start Firefox once you have at least another profile. To start it manually, you have two options : the CLI and the about: page.

Starting the profile manager with the CLI

to start the profile manager, call firefox from the via the command line with the -ProfileManager (or -P, or -p) option. How to do that depends on your OS.

On MacOS, use :

/Applications/Firefox.app/Contents/MacOS/firefox-bin -P

You might want to alias that, as the browser's cli has other interesting options (try -h).

On windows, I'm not sure what the path to Firefox is and it can varies, but same principle :

drive:\path\to\firefox\firefox.exe -P.

And if you're using Linux it depends on the distro, but there's a good chance firefox is already in your PATH so just firefox -P should work.

Using the about: page

It's as easy as browsing to about:profiles)`.

Note that two options will be unavailable from the about: page :

  • starting an "offline mode" session (with no Internet access)
  • set a default profile (avoids having to select a profile when the browser starts)