Regular Expression Syntax Cheat Sheet

Regular expressions (regex or regexp) are a pattern of characters that describe an amount of text.

Anchors

Anchors match a position before or after other characters.

Syntax	Description	Example pattern	Example matches	Example non-matches
`^`	match start of line	`^r`	`r`abbit `r`accoon	parrot ferret
`$`	match end of line	`t$`	rabbi`t` foo`t`	trap star
`\A`	match start of line	`\Ar`	`r`abbit `r`accoon	parrot ferret
`\Z`	match end of line	`t\Z`	rabbi`t` foo`t`	trap star
`\b`	match characters at the start or end of a word	`\bfox\b`	the red `fox` ran the `fox` ate	foxtrot foxskin scarf
`\B`	match characters in the middle of other non-space characters	`\Bee\B`	tr`ee`s b`ee`f	bee tree

Rather than matching specific characters, you can match specific types of characters such as letters, numbers, and more.

Syntax	Description	Example pattern	Example matches	Example non-matches
`.`	Anything except for a linebreak	`c.e`	`cle`an `che`ap	acert cent
`\d`	match a digit	`\d`	`6060`-`842` `2`b`\|`^`2`b	two **___
`\D`	Match a non-digit	`\D`	`The` 5 `cats ate` 12 `Angry men`	52 10032
`\w`	Match word characters	`\wee\w`	tr`ees` b`ee4`	The bee eels eat meat
`\W`	Match non-word characters	`\Wbat\W`	At `bat` Swing the `bat` fast	wombat bat53
`\s`	Match whitespace	`\sfox\s`	the `fox` ate his `fox` ran	it’s the fox. foxfur
`\S`	Match non-whitespace	`\See\S`	tr`ees` `beef`	the bee stung The tall tree
`\metacharacter`	Escape a metacharacter to match on the metacharacter	`\.` `\^`	The cat ate`.` 2`^`3	the cat ate 23

Character classes are sets or ranges of characters.

Syntax	Description	Example pattern	Example matches	Example non-matches
`[xy]`	match several characters	`gr[ea]y`	`gray` `grey`	green greek
`[x-y]`	match a range of characters	`[a-e]`	`a`m`be`r `b`r`a`n`d`	fox join
`[^xy]`	Does not match several characters	`gr[^ea]y`	`green` `greek`	gray grey
`[\^-]`	match metacharacters inside the character class	`4[\^\.-+*/]\d`	`4^3` `4.2`	44 23

Rather than matching single instances of characters, you can match repeated characters.

Syntax	Description	Example pattern	Example matches	Example non-matches
`x*`	match zero or more times	`ar*o`	cac`ao` c`arro`t	arugula artichoke
`x+`	match one or more times	`re+`	g`ree`n t`ree`	trap ruined
`x?`	Match zero or one times	`ro?a`	`roa`st `ra`nt	root rear
`x{m}`	match m times	`\we{2}\w`	`deer` `seer`	red enter
`x{m,}`	match m or more times	`2{3,}4`	671-`2224` `2222224`	224 123
`x{m,n}`	match between m and n times	`12{1,3}3`	`123`4 `12223`84	15335 1222223
`x*?, x+?, etc.`	match the minimum number of times - known as a lazy quantifier	`re+?`	t`re`e f`re`eeee	trout roasted

In order to extract specific parts of a string, you can capture those parts, and even name the parts that you captured.

Syntax	Description	Example pattern	Example matches	Example non-matches
`(x)`	capturing a pattern	`(iss)+`	M`ississi`ppi mi`ss`ed	mist persist
`(?:x)`	create a group without capturing	`(?:ab)(cd)`	Match: `abcd` Group 1: `cd`	acbd
`(?<name>x)`	create a named capture group	`(?<first>\d)(?<scrond>\d)\d*`	Match: `1325` first: 1 second: 3	2 hello
`(x\|y)`	match several alternative patterns	`(re\|ba)`	`re`d `ba`nter	rant bear
`\n`	reference previous captures where n is the group index starting at 1	`(b)(\w*)\1`	`blob` `brib`e	bear bring
`\k<name>`	reference named captures	`(?<first>5)(\d*)\k<first>`	`51245` `55`	523 51

You can specify that specific characters must appear before or after you match, without including those characters in the match.

Syntax	Description	Example pattern	Example matches	Example non-matches
`(?=x)`	looks ahead at the next characters without using them in the match	`an(?=an)` `iss(?=ipp)`	b`an`ana Miss`issi`ppi	band missed
`(?!x)`	looks ahead at next characters to not match on	`ai(?!n)`	f`ai`l br`ai`l	faint train
`(?<=x)`	looks at previous characters for a match without using those in the match	`(?<=tr)a`	tr`a`il tr`a`nslate	bear streak
`(?<!x)`	looks at previous characters to not match on	`(?!tr)a`	be`a`r tr`a`nslate	trail strained

Modifiers are settings that change the way the matching rules work.

Syntax	Description	Example pattern	Example matches	Example non-matches
`\Qx\E`	match start to finish	`\Qtell\E` `\Q\d\E`	`tell` `\\d`	I’ll tell you this I have 5 coins
`(?i)x(?-i).`	set the regex string to case-insensitive	`(?i)te(?-i)`	s`T`ep `tE`ach	Trench bear
`(?x)x(?-x)`	regex ignores whitespace	`(?x)t a p(?-x)`	`tap` `tap`dance	c a t rot a potato
`(?s)x(?-s)`	turns on single-line/DOTALL mode which makes the “.” include new-line symbols (\n) in addition to everything else	`(?s)first and second(?-s) and third`	`first and` `Second and third`	first and second and third
`(?m)x(?-m)`	changes ^ and $ to be end of line rather than end of string	`^eat and sleep$`	`eat and sleep` `eat and` `sleep`	treat and sleep eat and sleep.

Regular expressions can work beyond the Roman alphabet, with things like Chinese characters or emoji.

Code Points: The hexadecimal number used to represent an abstract character in a system like unicode.
Graphemes: Is either a codepoint or a character. All characters are made up of one or more graphemes in a sequence.

Syntax	Description	Example pattern	Example matches	Example non-matches
`\X`	match graphemes	`\u0000gmail`	`@gmail` www.email`@gmail`	gmail @aol
`\X\X`	match special characters like ones with an accent	`\u00e8 or \u0065\u0300`	`è`	e