Capture password protected sites
We basically only capture publicly available web pages, so if login is required we cannot make a screenshot of it.
Sometimes a workaround is possible, when you're in control of the server and can whitelist our IP-addresses so that our "screenshot engine" does not require a login. And for some logins, it works to put the username and password in the URL, like
https://username:email@example.com/. (Which is not advisable for very sensitive data, since you're sharing the login credentials. But it is considered acceptable to use for pages that you only protected so that Google doesn't index them.)