Why does Stack Exchange not allow signing in with a username?
86451
Are usernames required to be unique?
80208
Why doesn't Data Explorer log in with Stack Overflow login?
152941
username different in Terminal and System Preferences
52132
Why can't I use Stack Exchange if I'm under 13 years old, or if I'm under 16 years old and from the EU?
115608
Why not have one login to all stack subdomains?
88156
Can I set my user account to have no password?
15223
Is it OK to require users to have a third party login account?
30293
How a Gmail username can be taken but not recognised simultaneously?
143086
Cannot authenticate without a password
71310
User.Identity.IsAuthenticated is false after successful login
151084
Can I programmatically login a user without a password?
145773
How do I change my Stack Exchange password?
88786
My OpenID provider is shutting down; how do I change my Stack Exchange login?
116448
SignUp throws error in StackExchange.com for the non logged-in user
25495
Can't log in to the Stack Exchange app with a Google account
6252
Stack Exchange & Area 51 sign up/ log in update
98146
Login to Stack Exchange account doesn't use HTTPS/SSL?