Regex Cheat Sheet

Complete regular expression reference — anchors, quantifiers, groups, lookaheads, and flags.

Anchors

Pattern	Description	Example
^	Start of string (or line in multiline mode)	^Hello matches 'Hello world'
$	End of string (or line in multiline mode)	world$ matches 'Hello world'
\b	Word boundary	\bcat\b matches 'cat' but not 'catch'
\B	Non-word boundary	\Bcat matches 'scat'
\A	Start of string (no multiline)	\AHello
\Z	End of string (no multiline)	world\Z

Character Classes

Pattern	Description	Example
.	Any character except newline	a.c matches 'abc', 'a1c'
\d	Digit [0–9]	\d+ matches '42'
\D	Non-digit	\D+ matches 'abc'
\w	Word character [A-Za-z0-9_]	\w+ matches 'hello_42'
\W	Non-word character	\W+ matches ' '
\s	Whitespace (space, tab, newline)	\s+ matches ' '
\S	Non-whitespace	\S+ matches 'word'
[abc]	Character set — any of a, b, or c	[aeiou] matches vowels
[^abc]	Negated character set	[^aeiou] matches consonants
[a-z]	Character range	[a-z] matches any lowercase letter
[a-zA-Z]	Case-insensitive range	[a-zA-Z]+ matches 'Hello'

Quantifiers

Pattern	Description	Example
*	Zero or more (greedy)	a* matches '', 'a', 'aaa'
+	One or more (greedy)	a+ matches 'a', 'aaa'
?	Zero or one (optional)	colou?r matches 'color', 'colour'
{n}	Exactly n times	\d{3} matches exactly 3 digits
{n,}	n or more times	\d{2,} matches 2+ digits
{n,m}	Between n and m times	\d{2,4} matches 2–4 digits
*?	Zero or more (lazy)	a*? is non-greedy
+?	One or more (lazy)	<.+?> matches shortest tag
??	Zero or one (lazy)	colou??r — prefer no 'u'

Groups & Alternation

Pattern	Description	Example
(abc)	Capture group — captures match	(\d+) captures digits
(?:abc)	Non-capturing group	(?:https?://)\S+
(?P<name>abc)	Named capture group	(?P<year>\d{4})
a\|b	Alternation — a or b	cat\|dog matches 'cat' or 'dog'
\1	Backreference to group 1	(\w+)\s+\1 matches repeated words

Lookahead & Lookbehind

Pattern	Description	Example
(?=abc)	Positive lookahead — followed by	\d(?=px) matches digit before 'px'
(?!abc)	Negative lookahead — not followed by	\d(?!px) digit NOT before 'px'
(?<=abc)	Positive lookbehind — preceded by	(?<=\$)\d+ number after '$'
(?<!abc)	Negative lookbehind — not preceded by	(?<!\$)\d+ not after '$'

Flags

Pattern	Description	Example
g	Global — find all matches (not just first)	/\d+/g
i	Case-insensitive match	/hello/i matches 'HELLO'
m	Multiline — ^ and $ match line boundaries	/^start/m
s	Dotall — . matches newline too	/a.b/s matches 'a\nb'
u	Unicode — enables Unicode escapes	/\u{1F600}/u
y	Sticky — match at lastIndex only	/\d+/y
d	Indices — report match indices	/\d+/d

Special & Escape

Pattern	Description	Example
\n	Newline	line1\nline2
\t	Tab	col1\tcol2
\r	Carriage return	\r\n (Windows line ending)
\uXXXX	Unicode code point	\u0041 matches 'A'
\xHH	Hex code point	\x41 matches 'A'
\0	Null character	\0 (byte 0x00)
\\	Literal backslash	C:\\path matches 'C:\path'

Using this regex cheat sheet

Regular expressions are patterns used to match character combinations in strings. Most engines support PCRE-style syntax: anchors, character classes, quantifiers, groups, and lookaheads. JavaScript adds the g, i, m,s, u, and y flags via the RegExp object.

To test a regex against sample text, use the Regex Tester. To visualize how a pattern matches, try the Regex Visualizer. To escape special characters, see Regex Escape Tool.

Private & free — this tool runs entirely in your browser.