If you frequently switch between your normal version of Firefox and Nightly, you may experience profile corruption issues when browsing certain websites. A simple solution would be to have dedicated profiles for each of these channels. This article explains how to do this.

• For more information about creating and managing profiles, see the article Profile Manager - Create, remove or switch Firefox profiles.

• If you don't have Nightly installed on your computer: Download the installer for your language and system from the Firefox Nightly download page. You should wait until after you have created a dedicated profile before you launch Nightly.

The following steps are for Firefox Nightly but you can use the same procedure to create dedicated profiles for other versions of Firefox.

Windows

1. Press +R on the keyboard. A Run dialog will open.
2. Enter firefox -ProfileManager and click OK. The Profile Manager (Choose User Profile) window will open.
3. Select Create profile…, name it Nightly and click Finish.
4. Remove the checkmark from the box, Use the selected profile without asking at startup. This causes the Profile Manager to appear at startup unless you use a custom shortcut to start Firefox with a specific profile.
5. Click Exit to close the Profile Manager.
6. You can now update the shortcut you use to start Firefox Nightly, so that it automatically opens with your new Nightly profile:
   • Right-click the Nightly icon on your desktop and select Properties.
   • In the Shortcut tab, update the Target: field by adding a space, then -P Nightly after the path to the Firefox Nightly executable, which in most cases, would be as follows:
     "C:\Program Files\Nightly\firefox.exe" -P Nightly
7. Do the same for the shortcut that starts your normal version of Firefox. In most cases, you can use an existing Firefox profile instead of creating a new one. The following example is for a profile named default:
   • Right-click the Mozilla Firefox icon on your desktop and select Properties.
   • In the Shortcut tab, update the Target: field by adding a space, then -P default after the path to the Mozilla Firefox executable, which in most cases, would be as follows:
     "C:\Program Files\Mozilla Firefox\firefox.exe" -P default

Default browser considerations

When Firefox is your default browser, HTML files, Internet shortcuts and links opened in other applications will start Firefox with the Profile Manager when the Use the selected profile without asking at startup box is not checked. If you have customized all of your Firefox shortcuts to launch with a dedicated profile, the next time your default Firefox browser is launched and the Profile Manager opens, you can select the profile you would normally use (such as default) and then checkmark the Use the selected profile without asking at startup box before you start Firefox. Warning: If you select a profile to use without asking, be very careful to only start Nightly or other Firefox versions with shortcuts customized to start with a dedicated profile.

Mac

1. Open the Terminal application.
2. Type or paste in the path to Firefox, followed by .app/Contents/MacOS/firefox -profilemanager. For example, if Firefox is installed in the recommended location, you would enter /Applications/Firefox.app/Contents/MacOS/firefox -profilemanager. Press Return to open the Profile Manager (Choose User Profile) window.
3. Select Create profile…, name it Nightly and click Done.
4. Remove the checkmark from the box, Use the selected profile without asking at startup. This causes the Profile Manager to appear at startup unless you start Firefox with a custom launcher.
5. Click Exit to close the Profile Manager.

Linux

1. Open the Terminal application.
2. Enter firefox -ProfileManager, and press Enter to open the Profile Manager (Choose User Profile) window.
3. Select Create profile…, name it Nightly and click Finish.
4. Remove the checkmark from the box, Use the selected profile without asking at startup. This causes the Profile Manager to appear at startup unless you start Firefox with a custom launcher.
5. Click Exit to close the Profile Manager.
6. If you want individual icons to launch specific profiles, you will need to set the command line for your new launcher. To do this, set the command text field to target the executable file, likely /usr/bin/firefox, and add the -P PROFILE_NAME parameter, replacing PROFILE_NAME with the name of the specific profile.

You can now start using Nightly safely with its own dedicated profile. If you are a Sync user, you can simply sign in to your Sync account on both release and Nightly instances of Firefox to have your full browsing data always with you. If you never used Sync before, here are directions on how to set it up.