Firefox Not Opening

If facing Mozilla Firefox not opening problem, first of all, you should see what message is being displayed. Different problems display different error messages. If other web browsers are still working during this error, check your connection settings, it may be that Firefox cannot access the Internet. Another reason might be that you recently installed the add-on or have troubleshoot themes and extensions. In a worse case, you may need to create a new Firefox profile, because a corrupted profile will always prevent Firefox from opening.

What are the specific error messages display for Firefox not opening?

When Firefox not opening the user may receive a message stating “An error occurred while opening the file …”, you can try to log in as an administrator. Go to the “firefox.exe” program file in Windows, right-click the file, and select “Run as administrator”. Many times, users have recently updated their software. In this case, they will receive the “XU Runner – Error …” message. In this case, after deleting the old Firefox installation directory, you can use other browsers to download and install the latest version of Firefox.

4 Easy Ways to Fix Firefox Not Opening Problem

  1. Change proxy settings

If Firefox not opening, but other browsers are operating normally, use the following steps to check the proxy settings:

  • Click the “Firefox” menu option at the top of the Firefox window, and then select “Options.”
  • Go to the “Advanced” tab and click the “Network” option.
  • Click the “Settings …” button in the “Connect” section of the window.
  • If you are not using a proxy, click “No proxy”.
  • If you are using a proxy, please refer to the web browser settings of other browsers or Microsoft’s proxy settings guide.
  • Close the “Connection Settings” window.
  • Click “OK” to exit.
  1. Check other connection settings

Many Internet security software (such as firewalls or antivirus programs) prevent Firefox from accessing the Web. Mozilla Support reported that the recently updated Internet security program also caused connection problems.

  • Check your firewall or software, and see that Firefox is not in the list of blocked applications.
  • Connection problems on some operating systems may also be caused by protocols that access the Internet (such as IPv6).
  • Disable IPv6 in Firefox.
  • Enter “about: config” in the address bar and Press Enter.
  • Click the “I will be careful, I promise!” Button on the warning page.
  • Enter about: config window.
  • Enter “network.dns.disableIPv6” in the search box.
  • Double-click the “network.dns.disableIPv6” button and set its value to “true” to disable IPv6
  1. Themes and extensions

Application themes can change the appearance of Mozilla Firefox, and extensions can add new features or enhance existing Firefox features. When the theme or extension is damaged, they can cause Firefox to fail to open. Open Firefox in safe mode. It will disable themes, extensions and hardware acceleration.

  1. Firefox profile settings

The user’s personal information is saved in the Profile Manager in the preferences. When these settings are damaged, delete your configuration file and create a new one. Please perform the following steps:

  • Close Firefox.
  • Press the “Windows + R” key on the keyboard.
  • Type “firefox.exe -p” in the “Run” dialog box.
  • Press Enter.
  • Choose the coruupt profile. Click “Delete Configuration File …”
  • Click the “Delete File” option.
  • Click the “Create Profile …” button in the Profile Manager.
  • Follow the instructions on the screen.