How to Fix Mozilla Firefox “This Connection Is Untrusted” Error

Mozilla Firefox is an open-source and the most preferred web browser for Internet surfing. When you try to open or browse any websites on Firefox, it always first verifies the site’s identity using the security certificate before it loads or reaches the website. In case this verification is rejected, Mozilla Firefox stopped working and shows you an untrusted connection error to notify that there is the security hazard. Though you can avoid the ‘This Connection Is Untrusted’ security alert and open the website, it’s still better to discover the cause, and then fix the difficulties, if possible. Before you consult the Firefox customer support, have a look at these workarounds.

Fix 1 – Check Technical Details

If your Firefox browser shows the ‘This Connection Is Untrusted’ warning, it also contains a link with additional information about the cause of the alert. Click on the link labeled as the ‘Technical Details’ to check the particular error code and cause why Firefox considers the connection to be possible risky. Check the error code details shown in your web browser to the list of errors on the official Mozilla page to find out the issues.

Fix 2 – Wrong Computer Clock

If you see the ‘Certificate expired on’ and the ‘Certificate will not be valid until’ errors, it indicates that you’re trying to visit the website with fault lies. If, however, such warnings are shown for all trusted sites you’re trying to open with Firefox, it is possible that the date on your PC is incorrect. Go to the Start screen, choose the ‘Desktop’ tile, and then open the date and time settings from the right corner of the taskbar. Click the ‘Change date and time’ settings icon, and then choose the ‘Change date and time’ to enter the right information. Click the ‘OK,’ and then the ‘Apply’ to set the correct time on your PC.

Note – If your Firefox browser is often occurring issues, you can try the following methods to troubleshoot and diagnose the Firefox problems.

Fix 3 – Corrupted Certificate File

Mozilla Firefox saves the details about security certificates under the cert8.DB file. If somehow, this file is damaged, it means your browser would recognize all security certificates as illegal.  If Firefox shows the untrusted connection alert and says that the certificate’s issuer is unidentified, it indicates about the corrupted file. Click on the Firefox menu located at the top of your browser, and then click the ‘Help’ tab. Click the ‘Troubleshooting Information’ section, followed by the ‘Show Folder’ option next to the ‘Profile Folder’ under the ‘Application Basics’ heading section. Right-click on the ‘Cert8.DB’ and choose the ‘Delete’ option from the context menu. Restart your browser to create the file again.

Fix 4 – Third-Party Programs Interference

Sometimes, other programs like the out-of-date versions of security solutions can create the untrusted connection warning if SSL scanning is activated. At this time, you have to either update the antivirus software to the new editions or turn off the SSL scanning from within the programs temporary. To discover whether the antivirus or firewall is resulting in the error, you need to click on the ‘I Understand the Risks’ on the security alert, and then click the ‘Add Exception’ link. Click the ‘View’ button next to the Certificate Status to find who delivered the certificate. The name of the firewall or security program is shown in the ‘Issued By’ section if any of them is causing the error.

However, if everything else troubleshooting solutions fail to fix the Firefox ‘This Connection Is Untrusted’ error, you should immediately call the experts on Mozilla customer care number to solve the problems.


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