Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!(?:.*[^\W\d_]){2})

Non-Capturing Group(?:.*[^\W\d_]){2}

{2}repeats the group contents below exactly 2 times:

.*any Unicode character (except for line terminators), repeated any number of times

Negated Character Class[^\W\d_]

\Wany character that is not a Unicode word character

\da Unicode decimal digit

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Negative Lookahead(?!(?:.*\d){2})

Non-Capturing Group(?:.*\d){2}

{2}repeats the group contents below exactly 2 times:

.*any Unicode character (except for line terminators), repeated any number of times

\da Unicode decimal digit

Negative Lookahead(?!(?:.*[_!@\#$*]){2})

Non-Capturing Group(?:.*[_!@\#$*]){2}

{2}repeats the group contents below exactly 2 times:

.*any Unicode character (except for line terminators), repeated any number of times

Character Class[_!@\#$*]

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

!the literal ! (33₁₀ / 41₈ / 21₁₆)

@the literal @ (64₁₀ / 100₈ / 40₁₆)

\#the literal # (35₁₀ / 43₈ / 23₁₆)

$the literal $ (36₁₀ / 44₈ / 24₁₆)

*the literal * (42₁₀ / 52₈ / 2A₁₆)

Character Class[\w!@\#$]{3}

{3}matches exactly 3 characters from the set below:

\wa Unicode word character

!the literal ! (33₁₀ / 41₈ / 21₁₆)

@the literal @ (64₁₀ / 100₈ / 40₁₆)

\#the literal # (35₁₀ / 43₈ / 23₁₆)

$the literal $ (36₁₀ / 44₈ / 24₁₆)

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

Detailed match information will be displayed here automatically.

25 tokens

^
  (?!(?:.*[^\W\d_]){2})
  (?!(?:.*\d){2})
  (?!(?:.*[_!@\#$*]){2})
[\w!@\#$]{3}
$

New

a1!
4B_
*x7

fails
ab!
BBB
*x_
a1!B

a1!
4B_
*x7

fails
ab!
BBB
*x_
a1!B