After I sign in on a Stackexchange affiliated website on Google chrome, I can then visit any other Stackexchange affiliated websites and I do not need to manually sign in. Google Chrome recognizes that I'm signed in on an SE affiliate and therefore, I'm presented a prompt that asks if I want to either: cancel the automatic sign in or join the community if I've never signed in before. How can I do this on Firefox? Also, I would like to know how to do this because it creates a complicated situation when I need to suggest to a newer user that they should ask their question on a different affiliate. I mean, it seems kind of sketchy to tell someone to "create a new account but make sure to use the same username and password". Like, that's how password stealing scams work. But with Google Chrome, it recognizes that SE sites are affiliated and so the username and password (or the cookie for the logged in session or whatever it is) is automatically and securely submitted to the other SE site without user input. There's less confusion and an extra layer of automatic verification that the user doesn't have to worry about. This follows the basic security practice of never submitting credentials after you're already signed in on Facebook or any other social media site — if you are already signed in to your account and you are requested to "sign in to facebook to continue" for example on another site or when opening a link, it should automatically sign you in when you refresh the page. If not, then it's likely a spoofed sign in dialog or cloned web page trying to steal your password. At the very least, it should autofill if it is a legit sign in dialog. But Firefox does not do this on SE affiliated websites and we basically have to create individual accounts, with the same username and password, on each SE website. I literally have to click to create a new account or sign in, go through my settings, copy my saved password from another SE site and submit that with my email. Lastly, this also applies to SE affiliates that don't have "stackexchange" in the URL such as Superuser and AskUbuntu. I can sign in on AskUbuntu and then when I go to Math Stackexchange or Superuser, I'm automatically signed in. In the screenshots, you can see how there is the option to "join this community" when using Google Chrome. This option doesn't exist when using Firefox. After joining, there's an additional confirmation prompt that explains about automatic sign in, which also does not happen on Firefox.