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Firefox shows up on the taskbar as open, but is not viewable

swift10
swift10
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Last week after an update Firefox quit working. It will appear to open with an icon on the taskbar and shows up in Task Manager as being active, but the window does not open so I can use the browser. I restarted my computer, uninstalled Firefox, deleted Firefox program folders, reinstall it, but it still does not work.

Last week after an update Firefox quit working. It will appear to open with an icon on the taskbar and shows up in Task Manager as being active, but the window does not open so I can use the browser. I restarted my computer, uninstalled Firefox, deleted Firefox program folders, reinstall it, but it still does not work.

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jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 25 Contributor
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When you hover the mouse pointer over the button on the Windows Taskbar, do you see a thumbnail for an open Firefox window, but the window is not displayable?

Sometimes the main Firefox window gets "off screen" somehow. You often can force it to appear on the screen by right-clicking the thumbnail image floating above the Taskbar and choosing Maximize. Does that work?

One possible cause for this is when the file which stores window sizes and positions has become corrupted. You can remove that file and Firefox will return to standard window sizing/positioning.

Method #1: If you can get a maximized window:

Open your current Firefox settings (AKA Firefox profile) folder using either

  • "3-bar" menu button > "?" Help > Troubleshooting Information
  • (menu bar) Help > Troubleshooting Information
  • type or paste about:support in the address bar and press Enter

In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

  • "3-bar" menu button > Exit
  • (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then scroll down and rename xulstore.json to something like xulstoreOLD.json just in case you need it later. If you see a file named localstore.rdf, it's obsolete and you can delete it so Firefox doesn't convert it at your next startup.

Start Firefox back up again. Do windows display normally again?

Method #2: If you cannot get a Firefox window at all:

Shut down Firefox by right-clicking the taskbar icon > Close Window or Close All Windows.

Using the Run dialog (windows key + R) or the Windows search box, type or paste the following and press Enter to drill down to the Profiles folder: 

%APPDATA%\Mozilla\Firefox\Profiles

Here you may see one folder -- in which case, double-click into that -- or more than one folder -- in which case, double-click into what looks like the most recently updated.

Scroll down and rename xulstore.json to something like xulstoreOLD.json just in case you need it later. If you see a file named localstore.rdf, it's obsolete and you can delete it so Firefox doesn't convert it at your next startup.

Start Firefox back up again. Do windows display normally again?

That mini-reset will hide the menu bar and bookmarks toolbar. You can use one of these methods to show the toolbar list and select the desired bars there:

  • right-click (on Mac Ctrl+click) a blank spot on the tab bar (or right-click the "+" button)
  • (menu bar) View > Toolbars
    On Windows, tap the Alt key to activate the menu bar temporarily.
  • in Customize mode > Toolbars button (see: Customize Firefox controls, buttons and toolbars)

To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list.