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Fix: Mozilla Firefox SSL Certificate Error

Are you facing SSL Certificate errors in Firefox on your computer? Learn how to troubleshoot and fix the issue with our detailed guide.

Mozilla Firefox allows secure and private connection between the websites and browser; however, it won’t allow loading the site if it detects any security flaws. That’s one reason it blocks the site with an invalid or failed SSL certificate and connection. Sometimes this detection can be falsely positive. Hence, we can try bypassing security to access these sites.

Fix: SSL Certificate Error on Firefox browser

A safe browsing environment is at the top of the priority queue for every user. In this regard, browsers such as Firefox have done their bits by incorporating different levels of enhanced tracking protection, but that is the job half done.

The websites are equally vital in securing the data between the client and server. Two of the most crucial aspects are that the websites should follow the HTTPS protocol and have an SSL Certificate.

The latter one, Secure Socket Layer, verifies that the transfer of data between two servers or servers and the user is taking place safely and securely.

If a site doesn’t have this certificate, there is a high chance of the data getting intercepted during the exchange process.

But what if a site doesn’t have this certificate?

In these cases, your browser will warn you and advise against proceeding. In the case of Firefox, you might get error messages such as the ‘Secure Connection Failed, This Connection is Untrusted’, among others.


Fortunately, a few workarounds exist through which you could fix these Mozilla Firefox SSL Errors. And in this guide, we shall make you aware of just that. So without further ado, let’s get started.

Clear SSL State

Sometimes, when a website updates its SSL state, it might take a while before it’s reflected on your end. The reason for that might be due to the accumulation of quite a few cached SSL data.

Likewise, corruption of these data could also lead to certificate-related issues. So in all these cases, you should consider deleting the stored SSL State of your PC.

Here are the steps to clear SSL State:

  1. Head over to the Start menu and search and open Internet Options.
  2. Switch to the Content tab, and click on the Clear SSL State command option.
    Clear SSL State in Windows OS Internet Properties settingIt shall refresh the SSL certifications for the websites it has stored.
  3. Hit on Apply followed by OK to close.

Now launch Firefox, visit the concerned site, and check if the SSL Error has been fixed.

Deleting the SSL State wouldn’t adversely affect your interaction with that site. Instead, the next time you visit that website, the browser will re-scan for the available SSL certification and, if found, update its database accordingly. And this re-population of the data might fix the underlying issue as well.

Disable Firefox Proxy

If you use a Proxy server, the browser might not get the correct SSL certificate corresponding to your region and time zone. For the unaware, an incorrect time of the system is among the most common culprits for this issue.

When the publisher updates its SSL certificate, it might not sync with your PC if the latter uses an incorrect time zone. Therefore, you should consider disabling the Firefox proxy feature.

  1. Launch the Firefox browser on the computer.
  2. Click on the menu horizontal 3bar icon situated at the top right.
  3. Select the Settings menu from the list.
  4. Scroll to the Network Settings section.
    Mozilla Firefox Network Settings button
  5. Click to open Settings… button.
  6. Switch to No Proxy mode, and hit OK.
    Access internet without proxy in Mozilla Firefox

Now restart Mozilla Firefox and verify whether the SSL Error has been fixed.

Disabling a proxy might restrict your ability to browse geo-restricted content, but at the same time, it is equally essential to get hold of a site’s correct SSL state, so one shouldn’t hesitate for this trade-off.

Disable Antivirus Network Scan

If you get the SSL error across every other site you visit, it might have to do something with the antivirus software.

Sometimes, it might act slightly overprotective and raise a false flag, even if the site follows all the safety protocols.

To check or verify the same, you should consider disabling your antivirus network scan feature temporarily. If it fixes the underlying issue, it’s better to keep that functionality disabled.

With that said, here’s the list of major antivirus software and the network feature you need to disable/enable to fix the Mozilla Firefox SSL error.

Disable HTTPS scanning in the Antivirus software

  • Avast and AVG: Disable – Enable HTTPS Scanning.
  • Bitdefender: Disable – Encrypted Web Scan
  • Bullguard: Disable – Show safe results
  • ESET: Disable – SSL/TLS protocol filtering
  • Kaspersky: Enable – Do not scan encrypted connections

If turning off the network scan feature does rectify the issue, you should consider keeping that feature disabled. As far as online protection is concerned, you could consider using Windows Defender and Firewall applications.

Change Firefox SSL Settings

Apart from the Root Certificate each site needs, an additional intermediate certificate acts as a bridge between the root and your system. And every website also needs to give an equal weightage to this certificate.

If that is not the case, the browser might refuse to connect with that concerned site. While adding that certificate is in the developer’s hands, you could consider disabling the intermediate certificate check from your end.

Here are the steps to change the SSL check:

  1. Launch the Firefox browser, and head to the about:config page.
  2. Click on Accept the Risk and Continue command to proceed.
    Accept the Risk and Continue accessing the site in Firefox
  3. Search for security.ssl.enable_ocsp_stapling configuration.
  4. Change its value from True to False using the toggle switch.
    Disable security.ssl.enable_ocsp_stapling configuration in Firefox

Once done, restart the browser and see if it fixes the Mozilla Firefox SSL error.

While the intermediary certificate is used as a bridge between the root and the client, its importance cannot be neglected from a security point of view. Therefore, it’s usually better to enable that flag and disable it when accessing a site is crucial.

Manually Add Certificate

You may manually add the same to the browser if you have a valid and authorized CA. This way, you wouldn’t have to wait for the browsers to scan the site for the certification or stamp their approval. Here are the steps to add the certificate:

  1. Launch Mozilla Firefox for the computer.
  2. Open the Settings page from the More horizontal 3bar icon menu bar.
  3. Search for Certificates under the settings search bar.
    Search for Saved Certificate in Firefox browser
  4. Click on the View Certificate… button from the search results that appear.
  5. Switch to the Your Certificates section, and click Import… button.
    Import SSL Certificate in Mozilla Firefox
  6. Select the CA-approved certificate file from the local disk, and hit OK.

The SSL certificate will now be imported into the browser, and you may access the site without any issues.

Getting hold of a valid SSL certificate might be challenging, especially if you don’t have the required permissions. If that is the case with you, consider trying our other fixes mentioned here.

Bypass SSL Warning

Some sites have an SSL certificate incorporated in their sites, but any authority hasn’t approved that. Instead, they are self-signed certificates.

Some browsers, including Firefox, might receive an error message while encountering such a certificate. But at the same time, they also allow you to bypass this warning and access the required site.

So if you are pretty sure about the site’s validity and trustworthiness, and wish to bypass that error message, click on the Advanced… button next to the error message. After that, click on Accept the Risk and Continue, and you shall be taken to that site.

Mozilla Firefox Proceed with Unsecured Site with SSL

Do remember that accessing sites with a self-signed certificate might still possess some security risks, so only access them if it is of paramount importance.

Bottom Line

With this, we round off the guide on how you could fix the Mozilla Firefox SSL error. We have shared six potential fixes for this issue.

In my case, the site had updated its certification in the backend. However, it wasn’t getting reflected from my side. The issue was rectified after clearing the SSL cache stored on my PC.

Please let us know in the comments section which of the abovementioned troubleshooting steps managed to spell out success for you.

Lastly, if you've any thoughts or feedback, then feel free to drop in below comment box. You can also report the outdated information.

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Sadique Hassan

Sadique Hassan

Sadique is a Bachelor of Computer Application in Computer Science and an MBA professional. He became a tech writer by choice and has continued pursuing it for the last 7+ years. He is keenly interested in open-source technology like Android and also loves troubleshooting the tech. Connect with him on LinkedIn.

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