Firefox browser users appreciate its many features and seamless experience. But while it’s true that it’s one of the powerhouses in the world of browsers, it’s not always perfect.
Some have reported seeing the error code SEC_ERROR_REUSED_ISSUER_AND_SERIAL every time they try to access a certain local web browser or website.

Ways to Fix Firefox Browser Error Code SEC_ERROR_REUSED_ISSUER_AND_SERIAL
If you’re experiencing the same issue on Firefox, the good news is that there are a few solutions you can try to get rid of this annoying Firefox problem.
Restart Firefox and Reboot Your System
You can try to restart Firefox and check if doing so will remove the error code. It is especially the case if the error shows up as a result of a glitch.
But if nothing changes even after you’ve restarted the browser, you can also reboot the system itself. Many of the processes that may interfere with Firefox often stop after a restart.
Disable Your Firewall and Antivirus

One of the first steps you can take to get rid of the error code SEC_ERROR_REUSED_ISSUER_AND_SERIAL is to disable your firewall and antivirus in the meantime. Just so you know, these security measures are created to keep your device safe and secure from malicious attacks.
Sadly, there are times when they can interfere with the connection of your browser to the server of the specific website you’re trying to open. Disabling these features will allow you to establish a connection and sidestep the error.
Remove Invalid Certificates on Firefox Browser
Invalid certificates in Firefox can also sometimes meddle with the browser, resulting in the error code SEC_ERROR_REUSED_ISSUER_AND_SERIAL. Follow the steps below to delete these invalid certificates:
- Launch Firefox browser.
- Click the three horizontal lines to open the Settings menu.
- Proceed to the Privacy and Security option.
- Click View Certificates from the Certificates section.
- Choose a certificate.
- Click Delete.
Use a Different Browser
The SEC_ERROR_REUSED_ISSUER_AND_SERIAL in your Firefox browser might also be due to a temporary problem with the browser you’re using and sometimes, the best way to fix the issue is the most obvious one: use another browser.
But before you proceed, make sure that you try to re-launch Firefox first, as stated above, and see if this will clear the error.
Download a different browser and install it on your device. Launch the specific website that shows the error on the new browser to check if it will work this time.
Clear Firefox Cache and Browsing Data

Another possible remedy to the SEC_ERROR_REUSED_ISSUER_AND_SERIAL is to clear your cache and browsing data. Doing so will help eliminate any data stored previously.
As a result, it will clear up some space on the browser that might have been interfering with the connection and making the error show up.
Wrapping Up!
The SEC_ERROR_REUSED_ISSUER_AND_SERIAL error code on your Firefox browser is probably the last thing you’d want to see when you’re busy browsing or searching for important information.
Thankfully, there are several steps you can take to ensure that the error code will be gone for good and you can go back to your browsing experience all over again.