Regex Cheatsheet

Tokens, flags, and common patterns reference.

Tokens

.	Any character (except newline)
\d	Digit (0-9)
\D	Non-digit
\w	Word character (a-z, A-Z, 0-9, _)
\W	Non-word character
\s	Whitespace (space, tab, newline)
\S	Non-whitespace
^	Start of string (or line in multiline mode)
$	End of string (or line)
\b	Word boundary
\B	Non-word boundary
*	0 or more (greedy)
+	1 or more (greedy)
?	0 or 1, or makes a quantifier lazy
{n}	Exactly n
{n,}	n or more
{n,m}	Between n and m
[abc]	Any of a, b, or c
[^abc]	Anything except a, b, or c
[a-z]	Range a through z
(...)	Capturing group
(?:...)	Non-capturing group
(?=...)	Positive lookahead
(?!...)	Negative lookahead
(?<=...)	Positive lookbehind
(?<!...)	Negative lookbehind
a\|b	a or b
\1, \2	Back-reference to capture group 1, 2

Flags

/g	Global (find all matches)
/i	Case-insensitive
/m	Multiline (^ and $ match line breaks)
/s	Dotall (. matches newline)
/u	Unicode
/y	Sticky (match from lastIndex)

Common patterns

Email (simple)	[^\s@]+@[^\s@]+\.[^\s@]+
URL	https?:\/\/[^\s]+
IPv4	\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b
Phone (US)	$?\d{3}$?[\s.-]?\d{3}[\s.-]?\d{4}
Hex color	#?([a-fA-F0-9]{6}\|[a-fA-F0-9]{3})
Date (YYYY-MM-DD)	\d{4}-\d{2}-\d{2}
UUID	[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}
Slug	[a-z0-9]+(?:-[a-z0-9]+)*
Whitespace lines	^\s*$
Trailing whitespace	[ \t]+$

JavaScript flavor regex (POSIX flavor differs slightly). For the live tester, use the dedicated regex tester tool. For a deep dive, regular-expressions.info is the best free reference.

About

Quick reference for JavaScript regex: tokens (\d, \w, \b), quantifiers (*, +, ?), groups, lookarounds, and flags. Plus 10 ready-to-use patterns for email, URL, IPv4, etc.

How to use

Skim the table for what you need.

FAQ

Are these patterns production-ready?+

The simple ones (URL, IPv4) work for 90%+ of cases. Email regex is famously hard - the simple version misses edge cases but covers what you'd actually find in user input.