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How to start Firefox if you see an error message, "Firefox is already running, but is not responding" or, on Mac OS X, "A copy of Firefox is already open".

All of your personal settings, bookmarks, and other information are kept in your [[Profiles|Firefox profile]]. Firefox needs an unlocked profile to start up, and if the profile is locked, it displays the message, {for win,linux}''Firefox is already running, but is not responding''{/for}{for mac}''A copy of Firefox is already open''{/for}. This article explains what to do if you see this message and how to prevent it from showing at startup. {note}'''Note:''' If this is a recurring problem, see [[Firefox hangs or is not responding - How to fix#w_firefox-hangs-when-you-quit-it|Firefox hangs when you quit it]] for possible causes and solutions.{/note} {for mac}[[Image:FirefoxAlreadyOpen-Mac]]{/for} {for win} {for fx34,win7,win8,win10}[[Image:Fx34already-running-Win7]]{/for} {for fx34,winxp}[[Image:Firefox Already Running - Win1]]{/for} {for not fx34}[[Image:Firefox Already Running - Win1]]{/for} {/for} __TOC__ = End Firefox processes = <!-- see https://bugzilla.mozilla.org/show_bug.cgi?id=399108 and https://bugzilla.mozilla.org/show_bug.cgi?id=407981 on Firefox delayed shutdowns --> If Firefox did not shut down normally when you last used it, Firefox might still be running in the background, even though it is not visible. {for win7,win8,win10}If you try to open it while it's running, an error message will appear with the option to click {button Close Firefox}. If that doesn't solve the problem, restart your computer or try the following options.{/for} {for mac,linux,winxp}Restart your computer to see if the problem goes away or try the following options. {/for} {for linux} == Ubuntu Linux == # Click on {menu System} and choose {menu Administration}. # In Administration, click on {menu System Monitor}. Here you will find firefox-bin one or more times. # Highlight the listing and click {button End Process} for each one. {/for} {for win} == Use the Windows Task Manager to close the existing Firefox process == # Right-click on an empty spot in the Windows task bar and select {menu Task Manager} (or press {key Ctrl}+{key Shift}+{key Esc}). <!-- <br/> <br/> [[Image:notron360sucks-taksmanager.png]] <br/> <br/> --> # When the Windows Task Manager opens, select the {menu Processes} tab. #;[[Image:Task Manager]] # Select the entry for '''firefox.exe''' (press {key F} on the keyboard to find it) and click {button End Process}. # Click {button Yes} in the "Task Manager Warning" dialog that appears.<!-- <br/> <br/>[[Image:TaskMgrWarning.PNG]]<br/> --> # Repeat the above steps to end any additional firefox.exe processes, then exit the Windows Task Manager. # Start Firefox normally. {/for} = Remove the profile lock file = Firefox may have shut down abnormally, leaving the lock file in place. To fix this, open the profile folder (see [[Profiles - Where Firefox stores your bookmarks, passwords and other user data#w_finding-your-profile-without-opening-firefox|Finding your profile without opening Firefox]]) and delete the {for win}{filepath parent.lock} file{/for}{for linux} {filepath lock} and {filepath .parentlock} files{/for}{for mac}{filepath .parentlock} file{/for}. {for win} = Initialize the connection to a file share = If you store the profile on a file share, try accessing the file share beforehand using Windows Explorer. {/for} = Check access rights = Firefox must also have the right to create files in the profile folder. The error can occur if you try to use a profile from a file system mounted with read-only permission (e.g. a remote Windows share which doesn't have "Allow network users to change my files" checked). To check if the profile folder has the proper permissions: {for win} # Find your Firefox profile folder - see [[Profiles - Where Firefox stores your bookmarks, passwords and other user data#w_finding-your-profile-without-opening-firefox|Finding your profile without opening Firefox]]. #*If you only have one profile, its folder would have "default" in the name. # Right-click on your profile folder and select {menu Properties}. # Click on the {menu General} tab. #;[[Image:readonlyprofile.png]]<br/> # Make sure '''Read-only''' is not checked marked. {/for} {for mac} # Find your Firefox profile folder - see [[Profiles#w_finding-your-profile-without-opening-firefox|Finding your profile without opening Firefox]]. #*If you only have one profile, its folder would have "default" in the name # Hold down the {key Ctrl} key while you click on your profile folder, and select {menu Get Info}. # Make sure '''Ownership & Permissions''' is set to '''Read & Write'''. {/for} {for linux} #Find your Firefox profile folder - see [[Profiles#w_finding-your-profile-without-opening-firefox|Finding your profile without opening Firefox]] #*If you only have one profile, its folder would have "default" in the name. # Right-click on your profile folder and select {menu Properties}. # Click on the {menu Permissions} tab. # Make sure '''Folder access''' is set to '''Create and delete files'''. {/for} = Restore data from a locked profile = If you are unable to unlock the profile using the above methods, [[Use the Profile Manager to create and remove Firefox profiles|use the Profile Manager]] to create a new profile and migrate your data from the locked profile to the new profile. For information on how to do this, see [[Recovering important data from an old profile]]. <!-- MZ credit --> <br/> <br/> '''''Based on information from [http://kb.mozillazine.org/Profile_in_use Profile in use (mozillaZine KB)]''''' (In the following text, there is no formatting, because I don't know how to do that. Of course you can format it as you want.) How to prevent the error: Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system. when Firefox is running and we click on a link outside of Firefox. Tested on KDE on Fedora 31. kde menu > system > system settings > applications > default applications > web browser > (in the field: with the following command: write the following line: firefox -P myprofile --new-tab https://www.mozilla.org/ The URL after "--new-tab" is arbitrary. For example it could be the URL of the quick dial addon: moz-extension://51aa7b6f-86e3-48e7-b656-033db8c2b8f8/dial The name of the profile after "-P" is arbitrary, but it must exist. Optionally, we can write a path to firefox, as follows: /a/bin/installed/firefox_esr/firefox -P myprofile --new-tab https://www.mozilla.org/ How to prevent the same error when Firefox is running and we run it again. Right click the icon of Firefox > properties > application > command: (in this field, write the line show above;) (for example: firefox -P myprofile --new-tab https://www.mozilla.org/ )