By default, all browser instances use the same cookie for the same site. Is there a browser that doesn't follow this?

Or is there a Firefox plugin that can "wear" different cookies for a specific site?


IE versions 7 through 10 offer a "New Session" command which may do what you need (but it depends partly on how the site sets/uses its cookies). You can also set your IE shortcuts to automatically open in a new session by adding -nomerge to the end of the Target line.

Most current browsers also offer a "private" mode (IE Tools|InPrivate Browsing, Firefox Tools|Start Private Browsing, Chrome [wrench]|New incognito window, ...).

And as others have mentioned, in Firefox you can use profiles to achieve what you want.

  • adding to this, with IE, you can create AS MANY independent sessions as you want....chrome and FF will allow only 2(normal and private/incognito).. – tumchaaditya Mar 28 '13 at 3:00

Firefox has an extension that could do that:


Multifox is an extension that allows Firefox to connect to websites using different user names. Simultaneously!

For example, if you have multiple Gmail accounts, you can open them all at the same time. Each Firefox window, managed by Multifox, accesses an account without interfering each other

Each Multifox window is flagged with a number indicating the identity profile. Logins made in windows with different numbers are isolated.

Logins are preserved the same way they are in “regular” windows. Even if you close the window or quit Firefox.

The identity profile of each window is preserved when Firefox restores the session.

It can also easily switch between profiles:
enter image description here


If you are using Firefox (I assume you are since you mention it) you could just set up different profiles. Each profile has it's own set of cookies, plugins, configuration, etc.

I'm not sure you can run two instances at the same time on different profiles, but you haven't made it clear if that is also required.

First you need to access the Profile Manager by running firefox.exe -profilemanager, from here you can create any number of new profiles and rename those you already have.

Then you should untick the Don't ask at startup box, then the Profile Manager will appear every time you run Firefox, allowing you to select the profile you need everytime it starts.


Chrome and IE have "private" browsing modes that don't keep or send any cookies outside individual sessions. Depending on what you're trying to do that might be good enough.


Different Firefox profiles will use different sets of cookies.


If you are using IE8 google "Frame Merging". There's a command line switch and / or a registry fix that will allow you to have separate cookies for separate instances.


you can run two instance of firefox at the same time with "firefox -P -no-remote". each instance will have a different profile folder and so will not use the same cookies.


If you want to run a single instance of Firefox, you may be interested in the CookieSwap extension. In summary, it's a workaround, and the author considers what you want to be difficult to achieve.

If you have multiple logins for web based e-mail accounts (like Gmail and Yahoo! mail), then CookieSwap enables you to easily switch between those different user accounts by swapping the 'cookies' that the sites use to know your identity.

Note: When swapping profiles with CookieSwap, the cookies in all tabs and all browser windows are changed at the same time. This means that your web login to sites like gmail will change in all the tabs at once. I know it would be great to support different cookies per tab, but that problem poses some significant challenges.

In Google Chrome, incognito windows and non-incognito windows have separate sets of cookies. However, incognito windows have other side effects, and all incognito windows share the same sets of cookies (so you're limited to two identities in a single browser instance). Chrome also has a Swap My Cookies extension which is similar to Firefox's CookieSwap.

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