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How to start Firefox if you see an error message, "Firefox is already running, but is not responding" or, on macOS, "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 winxp,win7,win8}[[Image:Fx34already-running-Win7]]{/for} {for win10,win11}[[Image:Firefox 142_Firefox is already running_Windows 11]]{/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,win11}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 winxp,win7,win8} == 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:Windows 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 all additional firefox.exe processes, then exit the Windows Task Manager. # Start Firefox normally. {/for} {for win10,win11} == 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}). When the Windows Task Manager opens, it defaults to the {menu Processes} tab. #;{for win10}[[Image:Win10 Task Manager|width=620]]{/for}{for win11}[[Image:Windows 11_Task Manager_Firefox|width=620]]{/for} # Right-click the collapsible entry for Firefox{for win10} (press {key F} on the keyboard to find it){/for} and select {menu End Task} from the context menu. This will close all Firefox windows with no additional prompting. # Exit the Task Manager and 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}. = Remove the -no-remote startup option = If you start Firefox with th-e <code>-no-remote</code> [http://web.archive.org/web/20210530092017/https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options command line option], try removing this option. <!-- http://forums.mozillazine.org/viewtopic.php?f=38&t=3072986 --> {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 {for winxp,win7}Windows Explorer{/for}{for win8,win10,win11}File Explorer{/for}. {/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 ensure your profile folder has the proper permissions: {for win} # [[Profiles - Where Firefox stores your bookmarks, passwords and other user data#w_finding-your-profile-without-opening-firefox|Find your Firefox profile folder]]. # Right-click on your profile folder and select {menu Properties}. #;{for winxp,win7,win8}[[Image:readonlyprofile.png]]<br/>{/for}{for win10,win11}[[Image:Windows 11_Firefox profile properties_Read-only|width=400]]{/for} # In the {menu General} tab, {for winxp,win7,win8}make sure '''Read-only''' is ''not'' checked{/for}{for win10,win11}uncheck '''Read-only (Only applies to files in folder)''' (if it is not already){/for}. {/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, [[Profile Manager - Create, remove or switch 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)]'''''