[xx_ns]

bcrypt, one of the more popular password hashing algorithms out there, allows the password to be up to 72 characters in length. Any characters beyond that 72 limit are ignored and the password is silently truncated (!!!). It's actually a good method of testing whether a site uses bcrypt or not. If you set a password longer than 72 characters, but can sign in using just the 72 characters of your password, they're in all likelihood using bcrypt.

[integralid]

Yeah, that's why bcrypt is broken and shouldn't be used today. It had a good run, but nowadays we have better options like scrypt or argon2.

[daneel_w]

It's not broken. It's just potentially less helpful when it comes to protecting poor guessable passwords. bcrypt isn't the problem, weak password policies/habits are. Like bcrypt, argon2 is just a bandaid, though a tiny bit thicker. It won't save you from absurdly short passwords or silly "correct horse battery staple" advice, and it's no better than bcrypt at protecting proper unguessable passwords.

Also, only developers who have no idea know what they're doing will feed plain-text passwords to their hasher. You should be peppering and pre-digesting the passwords, and at that point bcrypt's 72 character input limit doesn't matter.