Remove Security Certificate Exceptions in Mozilla Firefox

Sometimes when you try to visit a website over a secure HTTPS connection, Firefox throws up a warning that the connection is untrusted. This may be due to a variety of reasons like invalid security certificate, expired security certificate, missing security certificate among others. If you want to open that website anyway, then you can add an exception to this website which causes Firefox to start trusting it irrespective of its security certificate status. You can add the security certificate exception either temporarily or permanently. If you add the exception temporarily, then the exception is valid only for the current Firefox session. But if you add the exception permanently, then it becomes valid everytime you use Firefox – which makes it a security risk. If you have added such a security exception, then you can remove it using the following steps.

Remove Security Certificate Exceptions in Firefox

  1. Open Mozilla Firefox web browser. Click on the orange colored Firefox button and choose Options → Options as shown in the picture below. This would open the Options window for Firefox.

    Remove Security Certificate Exceptions in Firefox

  2. When the Options window opens, click on the Advanced tab and then select the Encryption sub-tab. Under the Certificates category click on the View Certificates button as shown.

    Remove Security Certificate Exceptions in Firefox

  3. This would open the Certificate Manager window that shows a list of various kinds of certificates stored in Firefox. Choose the Servers tab which stores certificates for various websites. Scroll up and down the list and look for a server name (domain name) of website for which you added security exception. To remove that security certificate exception, select that domain and click on the Delete button. Please be careful that you do not delete some other certificate by mistake.

    Remove Security Certificate Exceptions in Firefox

  4. Go through the deletion process for all the server names (domain names) for which you have added exceptions. If you are doubtful about a domain whether you added exception for it or not, then just leave it alone.

Although you can add security certificate exceptions in Firefox to access some websites, it is not usually advised. The ‘untrusted connection’ warning in Firefox is there for a reason. If you continue with adding the exception, the data transfer to and from that website is not encrypted making you vulnerable to man-in-the-middle attacks. If you have already added such an exception, then you should remove it as soon as possible.


  1. How to do with current (June 2019) mobile version of Firefox? I’ve tried all of the “about:” pages and there is no way I see to access certificates on the mobile version.

  2. Update for Firefox, circa late 2016:

    Menu Button>Preferences Button>Advanced Button>Certificates Menu>View Certificates Button

    The one I wanted was under the “People” tab, but yours could be under others.

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