\d
Any digit (0-9)
\D
Non-digit
\w
Word char (a-z, A-Z, 0-9, _)
\W
Non-word char
\s
Whitespace
\S
Non-whitespace
.
Any char except newline
^
Start of string/line
$
End of string/line
*
0 or more
+
1 or more
?
0 or 1 (optional)
{n}
Exactly n times
{n,m}
Between n and m times
[abc]
Any of a, b, c
[^abc]
Not a, b, or c
(abc)
Capture group
(?:abc)
Non-capturing group
a|b
a or b
\b
Word boundary
\B
Non-word boundary
(?=abc)
Lookahead
Email
[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}
URL
https?://[^\s/$.?#].[^\s]*
IP Address
\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b
Phone (US)
[\+]?[1-9][\d]{9,14}