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Troubleshooting SSL Certificate Errors in Firefox: A Step-by-step Guide for Mozilla Users

If you’re seeing an SSL certificate error or a “Secure Connection Failed” message when trying to access a website in Firefox, it can be frustrating. SSL (Secure Sockets Layer) is a protocol used to establish an encrypted link between a web server and a browser, ensuring that all data passed between them remains private.

When there are issues with the SSL certificate, it can prevent you from accessing the site.

In this guide, we’ll walk through the most common causes of SSL connection errors in Firefox and provide step-by-step instructions on how to troubleshoot and fix them.

Whether you’re seeing an “invalid certificate” error, a “certificate error”, or other SSL-related issues, this post will help you get back to browsing securely.

Common SSL Errors in Firefox

There are a few different SSL certificate errors you may encounter in Firefox, including:


While the specific error codes may vary, they generally indicate an issue with the website’s SSL certificate or your browser’s ability to validate it. Some common causes include:

  • The website’s certificate has expired or is not yet valid
  • The certificate is self-signed or issued by an untrusted authority
  • Your computer’s date and time settings are incorrect
  • Antivirus or security software is interfering with the connection
  • The website doesn’t support the minimum TLS version required by Firefox

How to Fix SSL Certificate Errors on Firefox

Now that we understand some of the common SSL errors, let’s look at how to troubleshoot and resolve them:

1. Check Your Date and Time Settings

One of the most common causes of SSL certificate errors is incorrect date and time settings on your computer. SSL certificates have a valid date range, and if your system clock is off, it can cause Firefox to flag the cert as invalid.

To fix this:

  1. Open your computer’s date and time settings (in Windows, right-click the clock in the taskbar)
  2. Make sure the date, time, and time zone are all correct
  3. Enable the option to “Set time automatically” if available

2. Clear Your Browser Data

Outdated or corrupted browser data can sometimes interfere with secure connections. Try clearing your Firefox browsing history, cache, and cookies:

  1. Open the Firefox menu and select Options
  2. Go to Privacy & Security
  3. Under Cookies and Site Data, click “Clear Data”
  4. Check both “Cookies and Site Data” and “Cached Web Content”
  5. Click Clear and restart Firefox

3. Update Firefox

Using an outdated version of Firefox can cause compatibility issues with a website’s SSL certificate. Make sure you have the latest version installed:

  1. Open the Firefox menu
  2. Click Help > About Firefox
  3. Firefox will automatically check for and install any available updates

4. Disable Antivirus SSL Scanning

Some antivirus programs have a feature called “SSL scanning” or “HTTPS scanning” that can interfere with secure connections and cause errors. Try temporarily disabling this feature:

  • Avast: Open Avast settings, go to Protection > Web Shield > Customize, and uncheck “Enable HTTPS scanning”
  • Bitdefender: Open the dashboard, go to Protection > Online Threat Prevention > Settings, and toggle off “Encrypted Web Scan”
  • Consult your specific antivirus documentation for instructions

If disabling SSL scanning resolves the error, you may need to add an exception or permanently disable the feature for the affected site.

5. Bypass SSL Warnings (Use with Caution!)

If you’re certain a website’s SSL certificate is valid and you trust the site, you can bypass Firefox’s SSL warning message:

  1. When you see the warning page, click “Advanced”
  2. Click “Accept the Risk and Continue”

However, only do this if you are absolutely sure the website is legitimate and not compromised. Ignoring SSL warnings can put your data at risk.

6. Check the Certificate Details

If you’re encountering an “untrusted” or “invalid” certificate error, you can view the certificate details for more information:

  1. Click the padlock icon in the address bar
  2. Click “Connection secure” or “Connection not secure”
  3. Click “More information”
  4. Go to the Security tab and click “View Certificate”

Here you can see who issued the certificate, who it was issued to, and the valid date range. This may provide clues as to why Firefox doesn’t trust the cert.

7. Reset Your SSL/TLS Settings

In rare cases, your Firefox SSL and TLS settings may become misconfigured, causing secure connection failures. You can reset them to the defaults:

  1. Type about:config in the address bar and press Enter
  2. Click “Accept the Risk and Continue”
  3. Search for security.tls.version and security.ssl3
  4. Reset any changed values by right-clicking and selecting “Reset”

After resetting, restart Firefox and try accessing the site again.

Troubleshooting Site-Specific SSL Errors

If you’re encountering an SSL certificate error on just one particular site, there may be an issue with their SSL configuration rather than your browser. Some things to check:

  • Is your connection being intercepted by a firewall or security software? Temporarily disable these.
  • Does the site have a self-signed or expired certificate? Reach out to the site owner.
  • Is the site using an outdated SSL/TLS protocol version? They may need to update their server config.
  • Are you accessing the site on a public or corporate network that could be interfering? Try a different network.

You can also try accessing the problem site in a different browser like Chrome to compare the behavior. If it works in another browser, the issue is likely with your Firefox configuration. If you see the same error, the problem is likely on the website’s end.

When to Seek Additional Help

If you’ve worked through all the troubleshooting steps above and are still encountering SSL certificate errors in Firefox, don’t hesitate to seek additional help:

  • Search the Firefox support forum for threads about your specific error code
  • Post a new question describing your issue and what you’ve tried so far
  • Contact your antivirus or security software support for help with SSL scanning
  • Reach out to the website owner and let them know you’re having trouble with their SSL certificate

Remember, while SSL errors can be annoying, they’re ultimately there to protect your data and privacy.

Don’t ignore warnings or blindly bypass them without understanding the risks involved. With some patient troubleshooting using the steps outlined above, you should be able to resolve most common SSL certificate errors and get back to browsing securely in Firefox.

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