REFERENCE

Regex Cheatsheet

A complete reference for regular expression syntax. Bookmark this page — you'll come back to it.

Character Classes

Pattern	Description	Example
`.`	Any character except newline	a.c → abc, aXc
`\d`	Any digit (0-9)	\d+ → 123, 42
`\D`	Any non-digit	\D+ → abc, !@#
`\w`	Word character (letter, digit, underscore)	\w+ → hello_42
`\W`	Non-word character	\W → @, !, space
`\s`	Any whitespace (space, tab, newline)	\s → space, tab
`\S`	Any non-whitespace	\S+ → hello
`[abc]`	Any one of a, b, or c	[aeiou] → vowels
`[^abc]`	Any character except a, b, or c	[^0-9] → non-digits
`[a-z]`	Any character in range a to z	[a-zA-Z] → letters
`[0-9]`	Any digit (same as \d)	[0-9]{3} → 123

Pattern	Description	Example
`^`	Start of string (or line with m flag)	^Hello → starts with Hello
`$`	End of string (or line with m flag)	world$ → ends with world
`\b`	Word boundary	\bword\b → whole word
`\B`	Non-word boundary	\Bword → mid-word

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

Pattern	Description	Example
`g`	Global — find all matches	/regex/g
`i`	Case-insensitive	/hello/i → Hello, HELLO
`m`	Multiline — ^ and $ match line boundaries	/^line/m
`s`	Dotall — . matches newlines too	/a.b/s → a\nb
`u`	Unicode mode	/\p{Letter}/u
`v`	Unicode sets (extended)	/[\p{Letter}]/v
`d`	Generate indices for matches	match.indices
`y`	Sticky — match from lastIndex only	/regex/y