*

0 or more

{3}

Exactly 3

+

1 or more

{3,}

3 or more

?

0 or 1

{3,5}

3, 4 or 5

^

Start of string, or start of line in multi-line pattern

\A

Start of string

$

End of string, or end of line in multi-line pattern

\Z

End of string

\b

Word boundary

\B

Not word boundary

\<

Start of word

\>

End of word

?=

Lookahead assertion

?!

Negative lookahead

?<=

Lookbehind assertion

?!= or ?<!

Negative lookbehind

?>

Once-only Subexp­ression

?()

Condition [if then]

?()|

Condition [if then else]

?#

Comment

.

Any character except new line (\n)

(a|b)

a or b

(...)

Group

(?:...)

Passive (non-c­apt­uring) group

[abc]

Range (a or b or c)

[^abc]

Not (a or b or c)

[a-q]

Lower case letter from a to q

[A-Q]

Upper case letter from A to Q

[0-7]

Digit from 0 to 7

\x

Group/­sub­pattern number "­x"

\c

Control character

\s

White space

\S

Not white space

\d

Digit

\D

Not digit

\w

Word

\W

Not word

\x

Hexade­cimal digit

\O

Octal digit

\

Escape following character

\Q

Begin literal sequence

\E

End literal sequence

g

Global match

i *

Case-i­nse­nsitive

m *

Multiple lines

s *

Treat string as single line

x *

Allow comments and whitespace in pattern

e *

Evaluate replac­ement

U *

Ungreedy pattern

$n

nth non-pa­ssive group

$2

"­xyz­" in /^(abc­(xy­z))$/

$1

"­xyz­" in /^(?:a­bc)­(xyz)$/

$`

Before matched string

$'

After matched string

$+

Last matched string

$&

Entire matched string

^

[

.

$

{

*

(

\

+

)

|

?

< 

> 

[:upper:]

Upper case letters

[:lower:]

Lower case letters

[:alpha:]

All letters

[:alnum:]

Digits and letters

[:digit:]

Digits

[:xdigit:]

Hexade­cimal digits

[:punct:]

Punctu­ation

[:blank:]

Space and tab

[:space:]

Blank characters

[:cntrl:]

Control characters

[:graph:]

Printed characters

[:print:]

Printed characters and spaces

[:word:]

Digits, letters and underscore

\n

New line

\r

Carriage return

\t

Tab

\v

Vertical tab

\f

Form feed

\xxx

Octal character xxx

\xhh

Hex character hh

\l

Make next character lowercase

\u

Make next character uppercase

\L

Make entire string (up to \E) lowercase

\U

Make entire string (up to \E) uppercase

\u\L 

Capitalize first char, lowercase rest (sentence)