Your password has to meet four rules. The sign-up form checks each one as you type and ticks it off when it is met.
At least 8 characters. 72 is the maximum.
One lowercase letter — a to z.
One uppercase letter — A to Z.
One number — 0 to 9.
One special character. Any of these count: ! @ # $ % ^ & * ( ) _ + - = [ ] { } ; ' : " \ | , . < > / ?
Both password fields also have to match. The form tells you as soon as they do.
A password can be long and still fail — length alone is not enough. Check you have all four character types. The most common miss is the special character, and a space does not count as one.
Four unrelated words with a number and a symbol is easier to remember than a short scramble, and comfortably passes: river-Tuesday-92-lamp.
You do not need to meet these rules again to sign in — only to set a new password. See How to reset your password.
