Regex Cheatsheet

Complete regular expression cheatsheet and reference guide. Quick lookup for regex syntax, character classes, quantifiers, anchors, groups, lookaheads, and common patterns.

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Pattern	Description	Example	Match
.	Any character except newline	a.c	abc, aXc
\d	Any digit [0-9]	\d{3}	123, 456
\D	Any non-digit	\D+	abc, !@#
\w	Word character [a-zA-Z0-9_]	\w+	hello, var_1
\W	Non-word character	\W	!, @, #
\s	Whitespace (space, tab, newline)	a\sb	a b
\S	Non-whitespace	\S+	hello
[abc]	Any of a, b, or c	[aeiou]	a, e, i
[^abc]	Any character except a, b, or c	[^0-9]	a, Z, !
[a-z]	Any character in range a to z	[A-Z]	A, M, Z

Pattern	Description	Example	Match
^	Start of string (or line with m flag)	^Hello	Hello world
$	End of string (or line with m flag)	world$	Hello world
\b	Word boundary	\bcat\b	cat (not catch)
\B	Non-word boundary	\Bcat	scat (not cat)

Pattern	Description	Example	Match
*	0 or more (greedy)	ab*c	ac, abc, abbc
+	1 or more (greedy)	ab+c	abc, abbc
?	0 or 1 (optional)	colou?r	color, colour
{n}	Exactly n times	\d{4}	2024
{n,}	n or more times	\d{2,}	12, 123, 1234
{n,m}	Between n and m times	\d{2,4}	12, 123, 1234
*?	0 or more (lazy)	<.*?>	<b> in <b>text</b>
+?	1 or more (lazy)	a+?	a in aaa

Pattern	Description	Example	Match
(...)	Capturing group	(ab)+	ab, abab
(?:...)	Non-capturing group	(?:ab)+	ab, abab
(?=...)	Positive lookahead	\d(?=px)	3 in 3px
(?!...)	Negative lookahead	\d(?!px)	3 in 3em
(?<=...)	Positive lookbehind	(?<=\$)\d+	100 in $100
(?<!...)	Negative lookbehind	(?<!\$)\d+	100 in 100
\1	Back-reference to group 1	(\w+)\s\1	the the
$1	Replacement reference to group 1	s/(a)/[$1]/	[a]

Pattern	Description	Example	Match
g	Global — find all matches	/a/g	all a's in string
i	Case-insensitive matching	/hello/i	Hello, HELLO
m	Multiline — ^ and $ match line boundaries	/^a/m	a at line start
s	Dotall — . matches newlines	/a.b/s	a\nb
u	Unicode — full Unicode support	/\u{61}/u	a
y	Sticky — match from lastIndex only	/a/y	a at lastIndex

Pattern	Description	Example	Match
[\w.+-]+@[\w-]+\.[\w.]+	Email address	user@example.com	user@example.com
https?://[\w\-._~:/?#\[\]@!$&'()*+,;=%]+	URL	https://example.com	https://example.com
\+?[\d\s\-().]{7,15}	Phone number (international)	+1 (555) 123-4567	+1 (555) 123-4567
\b\d{1,3}(\.\d{1,3}){3}\b	IPv4 address	192.168.1.1	192.168.1.1
\d{4}-\d{2}-\d{2}	Date (YYYY-MM-DD)	2024-01-15	2024-01-15
#([0-9a-fA-F]{3}){1,2}\b	Hex color code	#ff6600, #f60	#ff6600
<([a-z]+)[^>]>.?</\1>	HTML tag (simple)	<div>text</div>	<div>text</div>
\b\d{4}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b	Credit card number	1234 5678 9012 3456	1234 5678 9012 3456

How to use Regex Cheatsheet

1. Browse sections. Scroll through character classes, anchors, quantifiers, groups, flags, and common patterns.
2. Search for a pattern. Use the filter box at the top to quickly find the regex syntax you need.
3. Copy a pattern. Click the copy button next to any entry to copy the pattern to your clipboard.

FAQ

What regex flavor does this cover?

This cheatsheet covers JavaScript/ECMAScript regex syntax, which is widely compatible with other languages including Python, Java, and C#.

What is the difference between greedy and lazy quantifiers?

Greedy quantifiers (*, +) match as much as possible. Lazy quantifiers (*?, +?) match as little as possible. Use lazy when you want the shortest match.

What are lookaheads and lookbehinds?

Lookahead (?=...) and lookbehind (?<=...) assert that a pattern exists ahead or behind the current position without including it in the match. Negative versions (?!...) and (?<!...) assert absence.

Regex Cheatsheet

Character Classes

Anchors

Quantifiers

Groups & References

Flags

Common Patterns

How to use Regex Cheatsheet

FAQ

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