I'd like to test my website as different users simultaneously, ideally on Firefox. Currently the only ways I know of doing this are

  1. Using different browsers
  2. Using profiles with FF

It's frustrating using FF profiles as you have to reinstall all your development plugins, which then each need to update individually. What I'm really looking for is a simple developer tool that lets me open a FF window that keeps its cookies completely separate from the main FF instance. Ideally it would also make that window stand out in some way to help me differentiate, but that I can live without ;)

Any ideas?

3 Answers 3


I haven't used it, but this extension looks like it does what you want: http://br.mozdev.org/multifox/

  • Ah, that looks perfect! Thanks! Will test and report back.
    – Andy
    Commented Mar 24, 2011 at 12:48
  • Yup it works! It allows numerous different 'identities', preserves their sessions, and indicates the identity in the address bar. Perfect.
    – Andy
    Commented Mar 24, 2011 at 12:54

Install Google Chrome and open the browser. Login as user one. Click File >> New Incognito Window. Login as user 2.

  • Nice idea thanks, but I'd like to stick to FF if at all possible.
    – Andy
    Commented Mar 24, 2011 at 12:50
  • You can use Private Browsing mode with Firefox, as described by Goboozo above for Chrome. That way you get two instances with more or less isolated/independent environments (cookies, logins, certificates, etc). Commented Aug 21, 2013 at 15:17

Firefox Multi-Account Containers seems to be the accepted solution for this nowadays.

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