Question

I need a regex to validate passwords with the following specs:

It must be between 6 and 20 characters with at least one upper case letter, one lower case letter and one digit

Answer 1

I think this works:

^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9]).{6,20}$

Here it is with test cases in Regex Hero.

The idea is to use positive lookaheads to ensure that at least one lower case letter, one upper case letter, and one digit are contained within the password. And then as a last step I simply specify a dot to allow any characters in the 6-20 character range.