It's risky for browsers to do it automatically since it's not something that sites are excepting. Some might be using different certificates on different server

It's risky for browsers to do it automatically since it's not something that sites are excepting. Some might be using different certificates on different servers for same domain for example. It's possible for sites to instruct browsers to do it though, but that's opt-in. https://en.wikipedia.org/w/index.php?title=HTTP_Public_Key_Pinning https://en.wikipedia.org/w/index.php?title=HTTP_Public_Key_P...