Hi, hold down the Shift key when you start Firefox to start in Safe Mode. More - Diagnose Firefox issues using Troubleshoot Mode.

If it works in Safe Mode, disable any theme and extensions - 3-bar menu > Add-ons > Themes/Extensions and restart Firefox; if it's OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some extensions.

If that doesn't work, try a Clean Reinstall; this means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location. With Firefox closed, use another browser to download Firefox from https://www.mozilla.org/en-US/firefox/all/ and save the file to somewhere convenient on your computer.

Now delete the Firefox installation folder which should be in one of the following locations -

C:\Program Files\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox

You can now double click the file you previously downloaded to install Firefox.

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

I tried the Uninstall and Reinstall and the result is the same: The Firefox icon appears in the task bar at the bottom of the screen. When I click on it it opens, but still in the Task Bar, making it useless. How do I get Firefox to open in the regular screen?

Hello AXtel17664, It sounds like your quick launch shortcut is somehow corrupted. Navigate to :

C:\Users\<YourName>\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar

and delete the quick launch shortcut. Then create a new shortcut and pin it to your taskbar.

Note: the AppData folder is a hidden folder. You may need to change your View setting in windows explorer.

This didn't solve the problem. Why am I looking at a folder for Internet Explorer when my problem is with Firefox? All I want to do is to get Firefox to open in full screen when I click on the icon on my main screen or in the task bar.

Hi I have same problem. In fact I opened a post for same issue a couple of hours ago and the suggestion is to do a clean install as well. I click on the Firefox icon in the task bar, in the start menu or a shorcut on the desktop and the result is ever the same: FIREFOX does not open.

Flipping hell, its quality degrades by the minute. At least I am not the only one! If that is some comfort......

It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application. Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/en-US/kb/server-not-found-connection-problem
• https://support.mozilla.org/en-US/kb/Firewalls
• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

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

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

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

I have the impression that moderators keep sending us "copy and paste" templated answers. We tell them: "they did not work" and nevertheless they send us more "copy and paste" replies. Nobody or very few seem to sit and give a customised written from scratch response. Sad.

The issue was solved. My computer was overrun with adware. It not only caused this Firefox problem, but also caused Norton AntiVirus to stop working. Adware was removed and now all is back to normal.

Hi AXtel17664, Glad to hear that your issue is resolved.

To help prevent a recurrence, can I suggest this extension:

Malwarebytes Browser Extension

Glad to hear.

I ran a full scan using Avira Antivirus and had no detection. Are malware covered by Avira Antivirus?

If not, what anti malware can I use. The one suggested obviously I can't right now as it's an extension and FF is not opening, remember?

Please help! I've tried everything. I've spent about 8 days (no less than 35 hrs. total) trying to fix this.

I created a new profile; I uninstalled, reinstalled. did a refresh firefox thing. did a full clean reinstall, etc.

sometimes I make some tiny progress, get it open; but it reverts back to not being able to open.

I'm at my wits end!

I have windows 10 pro; 64 bit no viruses; I use malwarebytes premium; adaware, etc.

Hi FirefoxHelpPlease, since you posted a new question, let's all discuss over there: https://support.mozilla.org/questions/1271943

ok; will do