The window may have been moved outside of the viewing area.

Occasionally the Firefox window will get off screen. Here are three different approaches to getting that window into view. One of them should work!

Firefox Window "off screen" — Arrow Key Method

If you know that Firefox is off to a particular side, you can use the arrow keys to move it back on screen. You only need to move it far enough to be able to click the title bar and then you can drag it the rest of the way.

Make the Firefox tile active on the task bar and press this key combination to start moving the window:

Alt+Spacebar > M

(To clarify, that's Alt+Spacebar to open the window control menu, then the letter m to start moving the window.)

Press the arrow key for the direction you want to move the window, e.g., press the left arrow key to move the window left. Press the Enter key to complete the move.

Firefox Window "off screen" — Maximize + New Window Script Method

If Firefox is nowhere to be found but you know it's out there, try this method. Make the Firefox tile active on the task bar and press this key combination to maximize the window:

Alt+Spacebar > X

(To clarify, that's Alt+Spacebar to open the window control menu, then the letter x to maximize the window.)

If that works, try this:

(1) Copy the following line of code to the clipboard (it's all one line...):

newwin=window.open(window.location.href,"_blank","width=640,height=480,menubar,toolbar,personalbar");newwin.moveTo(0,0);

(2) In the maximized window, press Ctrl+Shift+K to open the web console.

(3) Press Ctrl+v to paste the line of code next to the caret (») then press Enter to run it. A new copy of that page should open in a window positioned at the top left of the screen.

(4) Switch back to the maximized window and close it first, before doing anything in the new window.

Firefox Window "off screen" — Remove Settings File

If you can't move or maximize Firefox, you can rename or delete the settings file that stores the last window position.

(1) Open your currently active Firefox settings folder (AKA Firefox profile folder). From the Start menu (Run box or search box), paste this into the search box and press Enter:

%APPDATA%\Mozilla\Firefox\Profiles

This should open a window showing one or more Firefox profile folders. If you have multiple folders, look for the most recent. Click into your profile folder.

(2) If Firefox is still running, right-click it on the Task Bar and Close all Windows.

(3) Wait a few moments for Firefox to finish updating files in your profile folder, then rename xulstore.json to something else, like localstore-bad.rdf or localstore.old. Alternately, you can delete the file.

(4) You're done with your profile folder and you can restart Firefox now.

Thanks for your help! The alt+spacebar ideas didn't do anything so I used task manager to close firefox and deleted the xulstore.json file. When I clicked on the taskbar icon to start firefox it looked like a window opened for a second and then disappeared. When I hover the mouse over the firefox icon I can see that firefox is open When I left click on it the preview window opens and I see my firefox homepage. When I left click on the preview window nothing happens. When I right click on the preview window the options menu opens but when I click on any of the options nothing happens. I'm lost. Any other ideas?

Try deleting xulstore.json again. Then reboot the computer.

That didn't help. Any other ideas?

Open a second window. Close the first window. Wait about 10 seconds. Then close the browser.

Thanks! Do you mean open a second Firefox window? I can't open any Firefox windows. It shows that it is open in the taskbar icon but I can't get it to open on the screen. If you mean something else please clarify. If you have any ideas about how I can open Firefox please help.

On the quick launch bar, right-click the Firefox icon and select Open New Window

You can create a new profile as a quick test to see if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)