If Firefox can't access a secure site (one that starts with '''https''') you will see an error page with the message, ''Secure Connection Failed'' {for fx66}or ''Did Not Connect: Potential Security Issue'' and a description of the error. *If you see the message,{for not fx66} ''Your connection is not secure''{/for}{for fx66}''Warning: Potential Security Risk Ahead''{/for}, see the article [[What do the security warning codes mean?]] instead. * To troubleshoot other error messages, see [[Websites don't load - troubleshoot and fix error messages]]. __TOC__ = 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. If Firefox cannot establish a secure connection, you will not be able to connect to the website and Firefox will display an error page. A ''Secure Connection Failed'' error will include a description of the error, an option to report the error to Mozilla and a {button Try Again} button, similar to the error page shown below: [[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.'' = Website issues = Some websites try using outdated (no longer secure) [http://wikipedia.org/wiki/Transport_Layer_Security ''TLS''] mechanisms in an attempt to secure your connection.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. {for fx66} == "Did Not Connect" errors == You may see a ''Did Not Connect: Potential Security Issue'' error page for certain other connection issues. For example, some websites require [https://developer.mozilla.org/docs/Web/HTTP/Headers/Strict-Transport-Security#Description HTTP Strict Transport Security] (HSTS) and will not allow you to access the site if Firefox cannot establish a secure connection. [[Image:Fx66SecError-DidNotConnect]] Click the {button More Information} button on the error page for technical information about the error. {/for} = 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.

If Firefox can't access a secure site (one that starts with https) you will see an error page with the message, Secure Connection Failed or Did Not Connect: Potential Security Issue and a description of the error.

• If you see the message, Your connection is not secureWarning: Potential Security Risk Ahead, see the article What do the security warning codes mean? instead.
• To troubleshoot 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. If Firefox cannot establish a secure connection, you will not be able to connect to the website and Firefox will display an error page.

A Secure Connection Failed error will include a description of the error, an option to report the error to Mozilla and a Try Again button, similar to the error page shown below:

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.

Website issues

Some websites try using outdated (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. 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 this article's section on Antivirus products for help with specific security products that can produce these errors, such as Avast, AVG and ESET software.

Alternatively, you can uninstall third-party security software and use Microsoft Security Essentials, the free antivirus offered by Microsoft for Windows 7.Alternatively, you can uninstall third-party security software and use Windows Defender, the built-in antivirus on Windows 8 and Windows 10.

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
  Error code: MOZILLA_PKIX_ERROR_KEY_PINNING_FAILURE

• Certificate contains the same serial number as another certificate
  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 Troubleshoot time-related errors on secure websites.

See What do the security warning codes mean? for information about other certificate errors and warnings.