Of course the browser can't know this. But one clue for the user is if there is a strict length limit. If you're going to hash my password to 16 characters any

Of course the browser can't know this. But one clue for the user is if there is a strict length limit. If you're going to hash my password to 16 characters anyway, why can't I type in 20? But if you're going to store it as plaintext, you need to limit what I input.