Regex cheatsheet

A searchable reference for JavaScript and PHP patterns.

Characters

.
Any character
Any character except a line break. With the s flag it matches line breaks too.
a.c matches abc, a-c
\d
Digit
A digit 0 to 9.
\d{4} matches 2025
\D
Not a digit
Any character that is not a digit.
\w
Word character
A letter, digit or underscore.
\w+ matches user_1
\W
Not a word character
Anything except a letter, digit or underscore.
\s
Whitespace
Space, tab, line break and similar.
\S
Not whitespace
Any non-whitespace character.
\h
Horizontal whitespacePHP only
A space or tab.
\R
Any line breakPHP only
Matches \n, \r\n or \r as one unit.
\n \r \t
Line feed, carriage return, tab
Control characters.
\xhh
Hex character
The character with hex code hh.
\x41 matches A
\uhhhh
Unicode characterJavaScript only
A character by its 4-digit code point.
\u00e9 matches é
\x{hhhh}
Unicode characterPHP only
A character by code point. Needs the u flag.
\x{1F600}
\p{L}
Unicode letter
Any letter in any language. Needs the u flag.
\p{L}+ matches Ünïcode
\p{Lu}
Uppercase letter
Unicode uppercase letters. Needs the u flag.
\p{N}
Unicode number
Any numeric character. Needs the u flag.
\p{Emoji}
EmojiJavaScript only
Emoji characters. Needs the u flag.

[abc]
Any of
One character from the set.
[aeiou] matches vowels
[^abc]
None of
One character not in the set.
[a-z]
Range
Any character in the range.
[0-9a-f] matches hex digits
[[:alpha:]]
POSIX classPHP only
Letters. Also :digit:, :alnum:, :space:, :upper:, :lower:, :punct:.

^
Start
Start of the text. With the m flag, start of each line.
$
End
End of the text. With the m flag, end of each line.
\b
Word boundary
Between a word character and a non-word character.
\bcat\b matches cat, not concat
\B
Not a word boundary
Anywhere that is not a word boundary.
\A
Start of subjectPHP only
Very start of the text, ignoring the m flag.
\z
End of subjectPHP only
Very end of the text.
\Z
End or before final newlinePHP only
End of the text, allowing one trailing line break.

*
Zero or more
Greedy: as many as possible.
a* matches '', a, aaa
+
One or more
Greedy: at least one.
\d+ matches 7, 2025
?
Optional
Zero or one.
colou?r matches color, colour
{n}
Exactly n
Exactly n times.
\d{3}
{n,}
n or more
At least n times.
{n,m}
Between n and m
From n to m times.
\d{2,4}
*? +? ??
Lazy
Add ? to match as few as possible.
<.+?> matches one tag at a time
*+ ++ ?+
PossessivePHP only
Match greedily and never give back. Prevents backtracking.

(abc)
Capture group
Groups text and remembers the match as $1, $2 and so on.
(\d+)-(\d+)
(?:abc)
Non-capturing group
Groups without remembering the match.
(?<name>abc)
Named group
Capture with a name. Reuse with \k<name>.
(?<year>\d{4})
(?P<name>abc)
Named group (PCRE)PHP only
Older PCRE syntax. (?<name>) also works in PHP 5.2.2+.
\1 \k<name>
Backreference
Matches the same text as an earlier group.
(\w)\1 matches aa, bb
a|b
Alternation
Matches a or b.
cat|dog
(?>abc)
Atomic groupPHP only
Matches once and never backtracks into the group.
(?i)
Inline flagPHP only
Turn on a flag from this point, such as (?i) for case-insensitive.
(?R)
RecursionPHP only
Matches the whole pattern again, for nested structures.

(?=abc)
Positive lookahead
Followed by abc, without consuming it.
\d+(?=px) matches 12 in 12px
(?!abc)
Negative lookahead
Not followed by abc.
(?<=abc)
Positive lookbehind
Preceded by abc.
(?<=\$)\d+ matches 5 in $5
(?<!abc)
Negative lookbehind
Not preceded by abc.
\K
Reset match startPHP only
Drops everything matched so far from the result.
foo\Kbar

i
Ignore case
Letters match in either case.
g
GlobalJavaScript only
Find all matches, not just the first. In PHP use preg_match_all.
m
Multiline
^ and $ match at each line.
s
Dot matches newline
Lets . match line breaks.
u
Unicode
Treat the pattern and text as Unicode. Needed for \p{...}.
y
StickyJavaScript only
Match only at lastIndex.
d
IndicesJavaScript only
Report start and end positions of each group.
v
Unicode setsJavaScript only
Stricter Unicode mode with set operations in classes.
x
ExtendedPHP only
Ignore whitespace and allow # comments in the pattern.
U
UngreedyPHP only
Swaps greedy and lazy quantifiers.
D
Dollar end onlyPHP only
$ matches only at the very end.

^\S+@\S+\.\S+$
Simple email
A basic shape check. Fully validating email needs more than a regex.
^\d{4}-\d{2}-\d{2}$
ISO date
Matches 2025-03-01. Does not check the date is real.
^#?([0-9a-fA-F]{3}|[0-9a-fA-F]{6})$
Hex color
Matches #fff and #1f5bd8.
^https?://[^\s/$.?#].[^\s]*$
URL
A simple http or https link.
^\s+|\s+$
Trim whitespace
Matches leading and trailing whitespace. Replace with nothing.
\s{2,}
Repeated whitespace
Two or more whitespace characters in a row.

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