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`