I want to test a group of sites to see if they accept TLS 1.0 connections. Many sources including https://support.mozilla.org/en-US/questions/1101896 say that you can force Firefox to send TLS 1.0 requests by setting security.tls.version.max to 1, and I have done this successfully in the past to test if a site supported TLS 1.0. (Sometimes a site allows access over TLS 1.0 but disables certain features such as submitting credit card numbers.) However, I am now getting inconsistent results when trying to do this. I set security.tls.version.max to 1 and restart the browser. Then I go to https://www.google.com/, click the padlock and navigate to more information, and it says "Connected encrypted (TLS_AES_128_GCM_SHA256, 128 bit keys, TLS 1.3)". Note, TLS 1.3. But I could swear the first time I loaded https://www.google.com/ the same dialog box said the connection was using TLS 1.0. Meanwhile other sites like https://wikipedia.org/ and https://twitter.com/ fail to load with SSL_ERROR_PROTOCOL_VERSION_ALERT. I understand why (they don't support TLS 1.0), but I don't understand why the connection to Google is showing TLS 1.3 in the same browser window. Is there some mechanism by which a site that initially accepts the TLS 1.0 connection, is then forcing Firefox to switch to 1.3, overriding the security.tls.version.max setting? That doesn't make sense but it's the only thing that seems consistent with observation. Thanks!