Lookahead assertion
+
Negative lookahead
+
Lookbehind assertion
+
Negative lookbehind
+
Once-only Subexpression
Condition [if then]
Condition [if then else]
Comment
Assertions
?=
?!
?<=
?!= or ?<!
?>
?()
?()|
?#
Letters, numbers and hyphens
Date (e.g. 21/3/2006)
jpg, gif or png image
Any number from 1 to 50 inclusive
Valid hexadecimal colour code
8 to 15 character string with at least one
upper case letter, one lower case letter,
and one digit (useful for passwords).
Email addresses
HTML Tags
0 or more
+
0 or more, ungreedy
+
1 or more
+
1 or more, ungreedy
+
0 or 1
+
0 or 1, ungreedy
+
Exactly 3
+
3 or more
+
3, 4 or 5
+
3, 4 or 5, ungreedy
+
Quantifiers
*
*?
+
+?
?
??
{3}
{3,}
{3,5}
{3,5}?
Any character except
new line (\n)
+
a or b
+
Group
+
Passive Group
+
Range (a or b or c)
+
Not a or b or c
+
Letter between a and q
+
Upper case letter
+
between A and Q
+
Digit between 0 and 7
+
nth group/subpattern
+
Ranges
.
(a|b)
(...)
(?:...)
[abc]
[^abc]
[a-q]
[A-Q]
[0-7]
\n
Global match
Case-insensitive
Multiple lines
Treat string as single line
Allow comments and
white space in pattern
Evaluate replacement
Ungreedy pattern
Pattern Modifiers
g
i
m
s
x
e
U
nth non-passive group
"xyz" in /^(abc(xyz))$/
"xyz" in /^(?:abc)(xyz)$/
Before matched string
After matched string
Last matched string
Entire matched string
Entire input string
Literal "$"
String Replacement (Backreferences)
$n
$2
$1
$`
$'
$+
$&
$_
$$
Escape Character
+
New line
+
Carriage return
+
Tab
+
Vertical tab
+
Form feed
+
Alarm
Backspace
Escape
Named Character
Special Characters
\
\n
\r
\t
\v
\f
\a
[\b]
\e
\N{name}
Metacharacters (must be escaped)
[
{
\
|
>
^
$
(
)
<
.
*
+
?
Items marked + should work in most
regular expression implementations.
Note
Ranges are inclusive.
Note
These patterns are intended for reference purposes and have not been extensively tested.
Please use with caution and test thoroughly before use.
Note
Control character
White space
Not white space
Digit
Not digit
Word
Not word
Hexadecimal character hh
Octal character xxx
Character Classes
\c
\s
\S
\d
\D
\w
\W
\xhh
\Oxxx
Upper case letters
Lower case letters
All letters
Digits and letters
Digits
Hexadecimal digits
Punctuation
Space and tab
Blank characters
Control characters
Printed characters
Printed characters and
spaces
Digits, letters and
underscore
POSIX Character Classes
[:upper:]
[:lower:]
[:alpha:]
[:alnum:]
[:digit:]
[:xdigit:]
[:punct:]
[:blank:]
[:space:]
[:cntrl:]
[:graph:]
[:print:]
[:word:]
Start of line
+
Start of string
+
End of line
+
End of string
+
Word boundary
+
Not word boundary
+
Start of word
End of word
Anchors
^
\A
$
\Z
\b
\B
\<
\>
Sample Patterns
([A-Za-z0-9-]+)
(\d{1,2}\/\d{1,2}\/\d{4})
([^\s]+(?=\.(jpg|gif|png))\.\2)
(^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$)
(#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?)
((?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,15})
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6})
(\<(/?[^\>]+)\>)
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