Firefox Won’t Open? Reliable Hacks To Fix This Instantly

Although Mozilla Firefox is one of the useful open-source browsers available worldwide, there are some users who encounter Firefox Won’t Open issues frequently.

When there is an issue in Firefox, some unusual errors pop up. You will witness a countless number of errors when the Firefox crashes and open.

These errors include Mozilla crash reporter, error while opening file for writing, XML Parsing Error: undefined entity Location, “Secure Connection Failed … uses an invalid security certificate”, and many more.

Therefore, if you recently encountered this Firefox won’t open issue, you can go through the proven hacks which we have mentioned in this informative content.

Possible Errors Which you Might Encounter

At times, you might run into the Firefox won’t open Windows 10 error. Here are some errors which you encounter when Firefox crashes:

  • Mozilla Crash Reporter – You will encounter the error message when the Firefox closes all of a sudden.
  • You will encounter the message marked as “Firefox is already running but is not responding” error if the Profile is locked.
  • There will not be any loaded profile. It will put up an error message stating “Your Firefox profile cannot be loaded. It may be missing or inaccessible”.
  • Unable to read the configuration file.
  • You might experience an error post software update which states that “XULRunner – Error: Platform version <x.x.x.x> is not compatible with minVersion <x.x.x.x>”. 
  • There might be an error in the Windows system that states “Error opening file for writing…” This generally takes place on the Windows system which asks you to log in to Firefox with the help of an administrator account.
  • There are certain additional errors which you may run into if there is a problem in extensions, themes or hardware accelerations. The error message states “XML Parsing Error: undefined entity Location” or “Secure Connection Failed … uses an invalid security certificate”.
  • Lastly, you might encounter an error when Firefox refuses to open.

Don’t Know how to Fix Firefox won’t Open Issue? Here are Some Useful Hacks

When the Firefox puts up the above error messages and thereby crashes on several versions like Windows 10/8/7 or Mac 10.9/10.10/10.11/10.12/10.13, follow this generic guideline to sort things out instantly.

Fix 1: Refreshing Firefox on Windows/Mac

Since we all are aware of the fact that a simple restart or refresh of Firefox can resolve most of the obvious issues, go through the under-mentioned steps quickly:

  1. In order to begin, you need to launch Firefox.
  2. Now, move to the Menu option.
  3. Press the option labeled as Help. After that, click on the option termed Troubleshooting Information.
  4. Furthermore, press the Refresh Firefox button.
  5. Then, choose the Finish option and after you are done.

Refreshing Firefox can easily restore the browser to the default state if you create a new profile folder for the settings as well as the personal information.

Fix 2: Start Firefox in the Safe Mode

The safe Mode feature helps the users to troubleshoot problems. If you use Firefox in Safe Mode, you can easily be able to deactivate extensions, themes as well as hardware accelerations.

If Firefox helps in restarting the browser using the Safe Mode, the crashing problem might take place owing to an extension, theme or hardware acceleration.

  1. First of all, open Menu. After that, you need to click on Help.
  2. Now, you have to select the Restart with Add-ons Disabled option. After that, press Restart.
  3. Now, you have to choose “Start in Safe Mode” in the popup window after you restart the Firefox.

Apart from this, you can move ahead and press the Shift key when the Firefox starts in Safe Mode.

Fix 3: Delete Incompatibility Add Ons

There are certain instances when Firefox won’t open owing to incompatible add-ons. If you encounter the issue of Firefox won’t start after you install an extension, theme or plugin, you need to delete it.

Therefore, just go through the below-mentioned steps to resolve it.

  1. First of all, click on the Menu button.
  2. Now, you have to activate the Add-on Manager tab. You can do so by clicking the Add-ons option.
  3. Then, you can choose the add-ons which you wish to delete from the “Extensions or Themes” panel.
  4. Finally, press the Remove button and then choose the Restart Now option.

Fix 4: Reinstall Mozilla Firefox

If the Firefox fails to open even after performing the above-mentioned solutions diligently, you have to reinstall Mozilla Firefox. First of all, you need to uninstall Mozilla Firefox.

And then, you have to install the correct version of Firefox from the official website. This procedure is capable of solving almost all the issues.


Hopefully, the above solutions help you to fix the Firefox not opening issue without any hassle. If you follow the prescribed steps properly, you will not encounter this error in the near future.

However, you can refer to the user guide to get a quick glance. But if the above solutions fail to remove this error, then you have to seek professional help which can be your last resort.

Nathaniel Villa
Nathaniel Villa