Regular Expression Syntax Cheat Sheet

Regular expressions (regex or regexp) are patterns used to match character combinations in strings.

Anchors

Anchors match positions within text, not actual characters.

Syntax	Description	Example pattern	Matches	Non-matches
`^`	Start of a line	`^r`	`r`abbit, `r`accoon	parrot, ferret
`$`	End of a line	`t$`	rabbi`t`, foo`t`	trap, star
`\A`	Start of a string	`\Ar`	`r`abbit (at start)	parrot, inner matches
`\Z`	End of a string	`t\Z`	rabbi`t` (at end)	trap, inner matches
`\b`	Word boundary (start or end of a word)	`\bfox\b`	the `fox`, red `fox`	foxtrot, foxskin
`\B`	Not a word boundary	`\Bee\B`	tr`ee`s, b`ee`f	bee, tree

Match specific categories of characters.

Syntax	Description	Example pattern	Matches	Non-matches
`.`	Any character except newline	`c.e`	`cle`an, `che`ap	acert, cent
`\d`	Digit (`0-9`)	`\d`	6`0`60, `2`b	two, words
`\D`	Non-digit	`\D`	The, cats, `ate`	52, 10032
`\w`	Word character `[a-zA-Z0-9_]`	`\wee\w`	tr`ees`, b`ee4`	bee, eels
`\W`	Non-word character	`\Wbat\W`	`bat`, `,bat.`	wombat, bat53
`\s`	Whitespace	`\sfox\s`	`fox`	fox., foxfur
`\S`	Non-whitespace	`\See\S`	tr`ees`, `beef`	tall tree, bee stung
`\x`	Escaped metacharacter (e.g. `\.`)	`\.`	`.` (literal dot)	dot

Define a set of characters or ranges to match.

Syntax	Description	Example pattern	Matches	Non-matches
`[xy]`	Match any character in set	`gr[ea]y`	`gray`, `grey`	green, greek
`[x-y]`	Match a character in range	`[a-e]`	`a`, `b`, `c`	`f`, `z`
`[^xy]`	Not any character in set	`gr[^ea]y`	`gruy`	gray, grey
`[\^-]`	Match a literal `^` or `-`	`4[\^.-]\d`	`4^3`, `4-2`	`44`, `23`

Match characters repeated a number of times.

Syntax	Description	Example	Matches	Non-matches
`x*`	0 or more	`ar*o`	`ao`, `arro`	art, arugula
`x+`	1 or more	`re+`	`ree`, `tree`	ruin, root
`x?`	0 or 1	`ro?a`	`ra`, `roa`	root, roar
`x{m}`	Exactly m	`e{2}`	`deer`, `sees`	red, enter
`x{m,}`	At least m	`2{3,}`	`2224`, `2222224`	`22`, `123`
`x{m,n}`	Between m and n	`12{1,3}3`	`123`, `1223`	`15335`, `1222223`
`x+?`	Lazy match (as few as possible)	`re+?`	`re`, `ree`	`reel`, `reeee`

Group patterns, name them, or refer back to them.

Syntax	Description	Example	Matches	Non-matches
`(x)`	Capturing group	`(iss)+`	`Mississippi`	mist, persist
`(?:x)`	Non-capturing group	`(?:ab)(cd)`	`abcd` (captures `cd`)	acbd
`(?<name>x)`	Named capture	`(?<a>\d)(?<b>\d)`	`25` => a=`2`, b=`5`	`x5`, `ab`
`(x	y)`	Alternation (or)	`(re	ba)`
`\1`	Backreference to group 1	`(b)(\w*)\1`	`bob`, `brib`	bear, bib
`\k<name>`	Named backreference	`(?<x>5)\d*\k<x>`	`51245`, `55`	523, 51

Match based on what’s before or after, without capturing it.

Syntax	Description	Example	Matches	Non-matches
`(?=x)`	Positive lookahead	`an(?=an)`	`banana`, `ananas`	`band`
`(?!x)`	Negative lookahead	`ai(?!n)`	`fail`, `bail`	`faint`, `train`
`(?<=x)`	Positive lookbehind	`(?<=tr)a`	`trail`, `track`	`streak`, `bear`
`(?<!x)`	Negative lookbehind	`(?<!tr)a`	`bear`, `stare`	`trail`, `strain`

Control the behavior of the pattern engine.

Syntax	Description	Example	Matches	Non-matches
`\Q...\E`	Escape entire literal block	`\Q{hello}\E`	`{hello}`	hello
`(?i)...(?-i)`	Case-insensitive within group	`(?i)te(?-i)`	`Teach`, `Test`	trench
`(?x)...(?-x)`	Ignore whitespace inside regex	`(?x)t a p(?-x)`	`tap`, `tapdance`	`t a p`, `ta p`
`(?s)...(?-s)`	Dot matches newline (DOTALL)	`(?s)first.*third(?-s)`	includes `\n`	multiline mismatch
`(?m)^...$`	Multiline mode for `^` and `$`	`^eat and sleep$`	full line matches	mid-line only

Work with extended character sets, including emoji and accents.

Syntax	Description	Example	Matches	Non-matches
`\X`	Match one grapheme cluster	`\X\X` on `🇺🇸`	full emoji flag	half emoji
`\uXXXX`	Unicode character by code point	`\u00e8` or `\u0065\u0300`	`è`	`e`