Firefox not installing for some reason – error [Solved]

Madalina Dinita
by Madalina Dinita
Former Managing Editor
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  • Truth to be told, things are far from pleasant when Firefox is not installing due to countless reasons.
  • To solve this issue, you can try to disable Windows Defender or run Firefox as an Administrator.
  • Another solution is to give a try to a completely different browser. Opera is known to easily install.
  • This article is just a part of our Firefox Troubleshooting Hub. Therefore, feel free to check it out.
Firefox not installing for some reason
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Some users probably encountered various problems when trying to install Mozilla Firefox on their PC. If you are one of them, do not be demoralized.

In this article, we’ll offer you a list of the most common installation problems for Mozilla Firefox as well as solutions to most error messages.

What to do if Firefox is not installing for some reason?

1. Consider switching to Opera

try out Opera

When Firefox fails to install and you lack the time or experience to apply the below steps, switching to Opera is the first thing to do.

We won’t get into a detailed description here, but suffice to say, no installing errors could show up if making such a choice.

Besides that, chances are to appreciate the additional functionality of Opera. Unlike Firefox, Opera is notable for its free and unlimited VPN, useful unit converters, and visual bookmark.

On top of these, expect to enjoy customizable Speed Dial, which consists of pinned tiles on your home screen.



Opera installs easily, offers sidebar extensions and even a built-in newsreader. That’s why it’s a worthy alternative to Firefox.
Get it free Visit website

2. Reinstall Firefox

Reinstall Firefox with Revo

Sometimes you won’t be able to update Firefox at all, and your Firefox install might get stuck with Failed to read the configuration file. Please contact your system administrator message.

If this happens, your mozilla.cfg file might be damaged, and in order to fix the problem, it’s advised to reinstall Firefox.

In addition to uninstalling the application, you also have to remove all leftover files from Firefox’s installation directory.

Doing this manually can be a tedious task, therefore it’s always better to use an uninstaller software tool such as Revo Uninstaller.

This tool will remove Firefox, but it will also remove all of its files and registry entries from your PC. Once the application is completely removed, reinstall it again and the problem should be resolved.

Revo Uninstaller

Revo Uninstaller

If Firefox install gets stuck, use this tool to remove all leftover files from Firefox’s installation directory.
Get it free Visit website

3. Check your permissions

  1. Press Windows Key + R and enter %localappdata%. Press Enter or click OK.
    Hmm for some reason we could not install Firefox
  2. Locate Temp folder, right-click it and choose Properties from the menu.
    Firefox install takes forever
  3. Select the Security tab from the top menu and click Edit.
    Firefox installer stuck on now installing
  4. Click on Add.
    Firefox won't install Windows 10
  5. In the white box write the word Users / click OK.
    Hmm for some reason we could not install Firefox
  6. Select Users from the Group or user names list and check Full control in Allow column. Now click Apply and OK to save changes.
    Firefox installer stuck on now installing

This problem occurs after a change of permission in the Temp folder for some software. To fix that, follow the above steps. After making these changes, try to install Firefox again.

In addition to changing the permissions, some users are suggesting to clear all directories from the Mozilla updates folder. To do that, just follow these steps:

  1. Go to the AppDataLocal directory.
  2. Now navigate to the Mozilla updates directory.
    Firefox won't install Windows 10
  3. If you see any folder in there, remove them and try to update Firefox again.

4.  Try to update the browser manually

  1. Click the Menu icon in the top right corner and choose Help from the menu.
    Hmm for some reason we could not install Firefox
  2. Now click About Firefox.
    Firefox install stuck on downloading
  3. A new window will now appear and Firefox will check for updates. If any updates are available, they will be automatically installed.
    Firefox install takes forever

Theoretically, Firefox is set to automatically install the updates, but sometimes various factors may prevent that. To check for updates manually, do the following:

5. Run Firefox as an Administrator

If Firefox install gets stuck on your PC, perhaps the issue might be related to the missing privileges. To fix this issue, it’s required to run the setup file as an administrator.

This is quite simple, and to do it, you just need to locate the setup file, right-click it and choose Run as administrator.
Firefox installer stuck on now installing

If you’re having problems updating Firefox, you just need to repeat these steps for firefox.exe and then try to update it again.

6. Check your security software

try out Bullguard

If Firefox install gets stuck on your Windows 10 PC, the issue might be your security software.

Sometimes certain antivirus features can interfere with your system, so it’s advised to disable these features. Here’s how to do that in many popular antivirus tools:


Here’s how to disable the secure connection feature from this antivirus:

  1. Open the dashboard of Avast
  2. Click on Settings > Active Protection > Customize.
  3. Uncheck the Enable HTTP Scanning box and click on the OK button to update this feature.

This should stop your antivirus from checking the security certificate of every website you access.


  1. Open the dashboard of Bitdefender. If you have the 2016 version, click on Modules. For an older version you must click on the Protection button.
  2. Click on the Web Protection button.
  3. Disable the Scan SSL feature.


For ESET all you have to do is to enable the SSL/TSL protocol filtering feature.

  1. Open ESET antivirus.
  2. Press F5 to open the Advanced setup menu.
  3. Click on Web and email button > SSL/TSL > Enable SSL/TSL protocol filtering >OK.
  4. Restart the computer to configure the antivirus filter.


Kaspersky has a function that can be disabled to stop filtering the websites and it is very easy to do this.

  1. Open the dashboard of the antivirus.
  2. Click on the Settings button from the bottom-left.
  3. Click on the Additional button > Network.
  4. If you are using the 2016 version, uncheck the Do not scan encrypted connections box from the Encrypted connections settings section. For an older version just, uncheck the Scan encrypted connections feature.
  5. Reboot your system to configure your antivirus software.

If disabling this feature doesn’t solve the problem, completely disable your antivirus. If the issue still persists, remove your antivirus and check if that helps.

In case that removing the antivirus solves the problem, this might be a perfect opportunity to consider switching to a different antivirus solution.

If you want an antivirus that won’t interfere with your system while providing great protection, you should consider switching to BullGuard, the best antivirus at this moment.



If you’re looking for an error-free antivirus, BullGuard is a top choice. Try it out right away!
$23.99/year Get it free

7. Disable Windows Defender

  1. Open Settings first. You can do that quickly by using Windows Key + I shortcut.
  2. Go to the Update & Security section.
    Hmm for some reason we could not install Firefox
  3. Click Open Windows Defender Security Center.
    Firefox install stuck on housekeeping
  4. Go to the Virus & Threat protection section.
    Firefox install takes forever
  5. Now click Virus & threat protection settings.
    Firefox installer stuck on now installing
  6. Locate the Real-time protection option and disable it. You can also disable other options if you want.
    Firefox won't install Windows 10

Even if you don’t use a third-party antivirus, sometimes Firefox install can get stuck on your PC.

This can be caused by Windows Defender, and in order to fix the problem, you need to disable it as described above.

After disabling this option, try to install Firefox again. If Firefox installs successfully, be sure to enable Windows Defender once again.

8. Download the full installer

full installer

In order to distribute Firefox faster, Mozilla offers two types of installers, standard and full. The difference between the two is their size.

The standard installer is lighter, so it needs to download the setup files in order to install Firefox. This can sometimes cause Firefox install to get stuck.

On the other hand, the full installer won’t download any additional files, and instead, it will install Firefox right away.

This is a simple solution, and many users reported that it works, so be sure to try it out. You can get the full Firefox installer right away.

If none of these methods helped you, we strongly recommend you to get in touch with the Support department of Mozilla.

Instead of doing that from the start, let us tell you a few more tips when encountering similar issues:

  • Hmm, for some reason we could not install Firefox – There are times when the installation procedure does not complete and users get this message. If that’s your case too, note that you can’t have the Firefox running during installation.
  • Firefox not installing on Windows 7 – If you’ve tried to install Firefox to no avail, check the setting to Prevent Accessibility Services from accessing your browser from the Privacy & Security panel.
  • Cannot install/reinstall Firefox keeps saying an old copy is running? – Uninstalling the old copy first isn’t always enough. Also, get rid of any leftovers and stubborn software with the help of the best uninstaller tools.
  • Firefox installer stuck on now installing – This is a common problem with Firefox, and it’s usually caused by your temporary files. To fix it, change the permissions of the Temp folder and check if that helps.
  • Firefox won’t install Windows 10 – This issue can sometimes be caused by your antivirus. To fix it, disable your antivirus and check if that helps.
  • Firefox install stuck on downloading, housekeeping – Sometimes this issue can appear while trying to install Firefox using the standard installer. According to users, the solution is to download and use the full installer.
  • Firefox install takes forever – If your Firefox installation is slow, you might be able to fix the problem simply by trying to run it as an administrator. After doing that, check if the issue is still there.

Editor’s Note: This post was originally published in July 2018 and has been since revamped and updated in July 2020 for freshness, accuracy, and comprehensiveness.

Editor's Note: This article was originally published in August 2016 and was revamped and updated in July 2020 for freshness, accuracy, and comprehensiveness.