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If Firefox can't access a secure (https) site you may get a "Secure Connection Failed" or "Did not Connect" page. Learn why and what to do.

This article explains why you may see a ''Secure Connection Failed'' {for fx66}or a ''Did Not Connect: Potential Security Issue''{/for} error page and what to do. *If you see a{for not fx66} ''Your connection is not secure''{/for}{for fx66}''Warning: Potential Security Risk Ahead''{/for} error page, see the [[What do the security warning codes mean?]] article. * To troubleshoot other error messages, see [[Websites don't load - troubleshoot and fix error messages]]. __TOC__ = Secure connection cannot be established = When a website tries 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. If Firefox cannot establish a secure ('''[https://wikipedia.org/wiki/HTTPS https]''') connection, you will not be able to connect to the website and Firefox will display an error page. == Secure Connection Failed == A ''Secure Connection Failed'' error page will include a description of the error, an option to report the error to Mozilla and a {button Try Again} button. [[Image:fx60SecureConnectionFailed-ErrorCode]] The error page will also include the following information: * ''The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.'' * ''Please contact the website owners to inform them of this problem.'' {for fx66} == Did Not Connect: Potential Security Issue == For some secure connection issues, you may see a ''Did Not Connect: Potential Security Issue'' error page. For example, some websites require [https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security#Description HTTP Strict Transport Security] (HSTS) and will not allow access with an insecure connection. [[Image:Fx66SecError-DidNotConnect]] This type of error page will include a description of the potential security threat, an option to report the error to Mozilla and a {button More Information} button to view technical details about the error. {/for} = Website issues = Some websites try using outdated (no longer secure) [http://wikipedia.org/wiki/Transport_Layer_Security ''TLS''] mechanisms in an attempt to secure your connection.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. <!-- See https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean/discuss/6480#post-13160 --> Contact the owners of the website and ask them to update their TLS version to a version that is still current and still secure. = Security software conflict = Security products that intercept secure connections by default can produce secure connection errors or warnings on secure websites. If you see these errors on multiple secure websites, updating your security product or modifying its settings may resolve the issue. See [[How to troubleshoot security error codes on secure websites#w_antivirus-products|this article's section on Antivirus products]] for help with specific security products that can produce these errors, such as [https://www.avast.com Avast], [https://www.avg.com AVG] and [https://www.eset.com ESET] software. {for win7}Alternatively, you can uninstall third-party security software and use [https://support.microsoft.com/help/14210/security-essentials-download Microsoft Security Essentials], the free antivirus offered by Microsoft for Windows 7.{/for}{for win8,win10}Alternatively, you can uninstall third-party security software and use Windows Defender, the [https://www.microsoft.com/windows/comprehensive-security built-in] antivirus on Windows 8 and Windows 10.{/for} <!-- commented out based on https://bugzilla.mozilla.org/show_bug.cgi?id=1468892#c50 --> <!-- Another workaround is to set Firefox not to try TLS 1.3: # [[T:aboutconfig]] # In the search box above the list, type or paste '''TLS''' and pause while the list is filtered # Double-click the {pref security.tls.version.max} preference to display a dialog where you can modify the value from '''4''' to '''3''' (or, in other words, from TLS 1.3 to TLS 1.2) and then click OK.--> = Other secure connection issues = 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. See these articles for information about specific certificate issues and error codes: *[[Certificate Pinning Reports]]<br>Error code: MOZILLA_PKIX_ERROR_KEY_PINNING_FAILURE *[[Certificate contains the same serial number as another certificate]]<br>Error code: SEC_ERROR_REUSED_ISSUER_AND_SERIAL *An incorrect system date can cause Firefox to detect that the website's security certificate is expired or invalid. See [[How to troubleshoot time related errors on secure websites]]. See [[What do the security warning codes mean?]] for information about other certificate errors and warnings.