Firefox

From Vault13KB

Development profile

To avoid the performance hit of development-related prefs and extensions, and to avoid borking your personal data, you can use a separate profile for development work.

You can run two instances of Firefox using separate profiles if you start Firefox with the -no-remote parameter. For example, the following command will run your development profile whether "normal" Firefox is already running or not. (Assuming your development profile is called "dev"):

On Windows:

start "" "%ProgramFiles%\Mozilla Firefox\firefox.exe" -no-remote -P dev

On Mac:

/Applications/Firefox.app/Contents/MacOS/firefox-bin -no-remote -P dev &

On Linux:

firefox -no-remote -P dev &

(Use the dialog box that Firefox presents to create the profile called "dev" if necessary.)

To run Firefox with default profile just run "firefox" or "firefox -P default", as usual.