REGEX to validate password that can't contain some caracters

byMR

December 14, 2021

I need to check if a password match the following rules:

At least 8 characters (lenth)
One capital letter
One lower letter
One number
One special char
Can’t contain ‘.’ or ‘_’ (tricky part)

For example:

Bft$ns2E => should match
H2od%^.,3 => should’t match (notice the ‘.’)

I tried this:

^(?=.*?[A-Z])(?=(.*[a-z]){1,})(?=(.*[\d]){1,})(?=(.*[\W]){1,})(?!.*\s).{8,}$

That satisfy all rules, except the last one ( Can’t contain ‘.’ or ‘_’). Regex are always a pain for me and can’t figure out how to do this.

Thanks to all!

>Solution :

Your regex is on the right track. I would use:

^(?=.*?[A-Z])(?=.*[a-z])(?=.*\d)(?=.*\W)(?!.*[._]).{8,}$

This pattern says to:

^
    (?=.*?[A-Z])  assert capital letter
    (?=.*[a-z])   assert lowercase letter
    (?=.*\d)      assert digit
    (?=.*\W)      assert non word/special character
    (?!.*[._])    assert NO dot or underscore
    .{8,}         match a password of length 8 or greater
$