If Firefox can't access a secure site (one that starts with https) you will see an error page with the heading Secure Connection Failed and a message about the error.

• If you see this heading without accessing a secure site, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

• For troubleshooting other error messages, see Websites don't load - troubleshoot and fix error messages.

Secure connection cannot be established

When a website you visit attempts to secure communication between your computer and the website, Firefox cross-checks this attempt to ensure that the certificate and the method the website is using are actually secure.

Some websites try using out-dated (no longer secure) TLS mechanisms in an attempt to secure your connection. Firefox protects you by preventing navigation to such sites if there is a problem in securely establishing a connection. When this happens, you will see an error page with the option to report the error to Mozilla.

Certificate warnings

Firefox uses certificates on secure websites to ensure that your information is being sent to the intended recipient and can't be read by eavesdroppers. For a list of certificate warnings and error codes, see the article "This Connection is Untrusted" error message appears - What to doWhat do the security warning codes mean?.