Regex Pal

Dan's Tools

Email address *screening* not validation

Screens out many forms of obviously invalid email addresses without attempting to fully validate an email address (which should be the function of an SMTP implementation). Hopefully does not exclude any valid email addresses at the expense of allowing some invalid addresses.

Comments

Top Regular Expressions

Cheat Sheet

Character classes
. any character except newline
\w \d \s word, digit, whitespace
\W \D \S not word, digit, whitespace
[abc] any of a, b, or c
[^abc] not a, b, or c
[a-g] character between a & g
Anchors
^abc$ start / end of the string
\b word boundary
Escaped characters
\. \* \\ escaped special characters
\t \n \r tab, linefeed, carriage return
\u00A9 unicode escaped ©
Groups & Lookaround
(abc) capture group
\1 backreference to group #1
(?:abc) non-capturing group
(?=abc) positive lookahead
(?!abc) negative lookahead
Quantifiers & Alternation
a* a+ a? 0 or more, 1 or more, 0 or 1
a{5} a{2,} exactly five, two or more
a{1,3} between one & three
a+? a{2,}? match as few as possible
ab|cd match ab or cd