How to check the what TLS version is used by a webserver?

TLS 1.3 (RFC 8446) is the new standard security protocol since August 2018. TLS is used by https:// connections.

Requirement: A browser that supports TLS 1.3, currently Firefox 61 is the only browser that supports it out of the box. Others are following soon.

This blog already is served by TLS 1.3 thanks to my hoster cyon.ch.

TLS 1.3 message in Firefox 61

You can find the protocol in Firefox if you click on the icon in the address bar beside the https://, then click ">" (Show connection details) and then click on "More information".

Or alternatively you can use developer tools by pressing F12, select "Network", reload the page, select the first line on the left side and finally select "Security" on the right side.

Firefox Developer Tools Security page