Quick-Start: Regex Cheat Sheet


The tables below are a reference to basic regex. While reading the rest of the site, when in doubt, you can always come back and look here. (It you want a bookmark, here's a direct link to the regex reference tables). I encourage you to print the tables so you have a cheat sheet on your desk for quick reference.

The tables are not exhaustive, for two reasons. First, every regex flavor is different, and I didn't want to crowd the page with overly exotic syntax. For a full reference to the particular regex flavors you'll be using, it's always best to go straight to the source. In fact, for some regex engines (such as Perl, PCRE, Java and .NET) you may want to check once a year, as their creators often introduce new features.

The other reason the tables are not exhaustive is that I wanted them to serve as a quick introduction to regex. If you are a complete beginner, you should get a firm grasp of basic regex syntax just by reading the examples in the tables. I tried to introduce features in a logical order and to keep out oddities that I've never seen in actual use, such as the "bell character". With these tables as a jumping board, you will be able to advance to mastery by exploring the other pages on the site.

How to use the tables

The tables are meant to serve as an accelerated regex course, and they are meant to be read slowly, one line at a time. On each line, in the leftmost column, you will find a new element of regex syntax. The next column, "Legend", explains what the element means (or encodes) in the regex syntax. The next two columns work hand in hand: the "Example" column gives a valid regular expression that uses the element, and the "Sample Match" column presents a text string that could be matched by the regular expression.

You can read the tables online, of course, but if you suffer from even the mildest case of online-ADD (attention deficit disorder), like most of us… Well then, I highly recommend you print them out. You'll be able to study them slowly, and to use them as a cheat sheet later, when you are reading the rest of the site or experimenting with your own regular expressions.

Enjoy!

If you overdose, make sure not to miss the next page, which comes back down to Earth and talks about some really cool stuff: The 1001 ways to use Regex.


Regex Accelerated Course and Cheat Sheet

For easy navigation, here are some jumping points to various sections of the page:

Characters
Quantifiers
More Characters
Logic
More White-Space
More Quantifiers
Character Classes
Anchors and Boundaries
POSIX Classes
Inline Modifiers
Lookarounds
Character Class Operations
Other Syntax


(direct link)

Characters

CharacterLegendExampleSample Match
\dMost engines: one digit
from 0 to 9
file_\d\dfile_25
\d.NET, Python 3: one Unicode digit in any scriptfile_\d\dfile_9੩
\wMost engines: "word character": ASCII letter, digit or underscore\w-\w\w\wA-b_1
\w.Python 3: "word character": Unicode letter, ideogram, digit, or underscore\w-\w\w\w字-ま_۳
\w.NET: "word character": Unicode letter, ideogram, digit, or connector\w-\w\w\w字-ま‿۳
\sMost engines: "whitespace character": space, tab, newline, carriage return, vertical taba\sb\sca b
c
\s.NET, Python 3, JavaScript: "whitespace character": any Unicode separatora\sb\sca b
c
\DOne character that is not a digit as defined by your engine's \d\D\D\DABC
\WOne character that is not a word character as defined by your engine's \w\W\W\W\W\W*-+=)
\SOne character that is not a whitespace character as defined by your engine's \s\S\S\S\SYoyo


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Quantifiers

QuantifierLegendExampleSample Match
+One or moreVersion \w-\w+Version A-b1_1
{3}Exactly three times\D{3}ABC
{2,4}Two to four times\d{2,4}156
{3,}Three or more times\w{3,}regex_tutorial
*Zero or more timesA*B*C*AAACC
?Once or noneplurals?plural


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More Characters

CharacterLegendExampleSample Match
.Any character except line breaka.cabc
.Any character except line break.*whatever, man.
\.A period (special character: needs to be escaped by a \)a\.ca.c
\Escapes a special character\.\*\+\?    \$\^\/\\.*+?    $^/\
\Escapes a special character\[\{\(\)\}\][{()}]


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Logic

LogicLegendExampleSample Match
| Alternation / OR operand22|3333
( … )Capturing groupA(nt|pple)Apple (captures "pple")
\1Contents of Group 1r(\w)g\1xregex
\2Contents of Group 2(\d\d)\+(\d\d)=\2\+\112+65=65+12
(?: … )Non-capturing groupA(?:nt|pple)Apple


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More White-Space

CharacterLegendExampleSample Match
\tTabT\t\w{2}T     ab
\rCarriage return charactersee below
\nLine feed charactersee below
\r\nLine separator on WindowsAB\r\nCDAB
CD
\NPerl, PCRE (C, PHP, R…): one character that is not a line break\N+ABC
\hPerl, PCRE (C, PHP, R…), Java: one horizontal whitespace character: tab or Unicode space separator
\HOne character that is not a horizontal whitespace
\v.NET, JavaScript, Python, Ruby: vertical tab
\vPerl, PCRE (C, PHP, R…), Java: one vertical whitespace character: line feed, carriage return, vertical tab, form feed, paragraph or line separator
\VPerl, PCRE (C, PHP, R…), Java: any character that is not a vertical whitespace
\RPerl, PCRE (C, PHP, R…), Java: one line break (carriage return + line feed pair, and all the characters matched by \v)


(direct link)

More Quantifiers

QuantifierLegendExampleSample Match
+The + (one or more) is "greedy"\d+12345
?Makes quantifiers "lazy"\d+?1 in 12345
*The * (zero or more) is "greedy"A*AAA
?Makes quantifiers "lazy"A*?empty in AAA
{2,4}Two to four times, "greedy"\w{2,4}abcd
?Makes quantifiers "lazy"\w{2,4}?ab in abcd


(direct link)

Character Classes

CharacterLegendExampleSample Match
[ … ]One of the characters in the brackets[AEIOU]One uppercase vowel
[ … ]One of the characters in the bracketsT[ao]pTap or Top
-Range indicator[a-z]One lowercase letter
[x-y]One of the characters in the range from x to y[A-Z]+GREAT
[ … ]One of the characters in the brackets[AB1-5w-z]One of either: A,B,1,2,3,4,5,w,x,y,z
[x-y]One of the characters in the range from x to y[ -~]+Characters in the printable section of the ASCII table.
[^x]One character that is not x[^a-z]{3}A1!
[^x-y]One of the characters not in the range from x to y[^ -~]+Characters that are not in the printable section of the ASCII table.
[\d\D]One character that is a digit or a non-digit[\d\D]+Any characters, inc-
luding new lines, which the regular dot doesn't match
[\x41]Matches the character at hexadecimal position 41 in the ASCII table, i.e. A[\x41-\x45]{3}ABE


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Anchors and Boundaries

AnchorLegendExampleSample Match
^Start of string or start of line depending on multiline mode. (But when [^inside brackets], it means "not")^abc .*abc (line start)
$End of string or end of line depending on multiline mode. Many engine-dependent subtleties..*? the end$this is the end
\ABeginning of string
(all major engines except JS)
\Aabc[\d\D]*abc (string...
...start)
\zVery end of the string
Not available in Python and JS
the end\zthis is...\n...the end
\ZEnd of string or (except Python) before final line break
Not available in JS
the end\Zthis is...\n...the end\n
\GBeginning of String or End of Previous Match
.NET, Java, PCRE (C, PHP, R…), Perl, Ruby
\bWord boundary
Most engines: position where one side only is an ASCII letter, digit or underscore
Bob.*\bcat\bBob ate the cat
\bWord boundary
.NET, Java, Python 3, Ruby: position where one side only is a Unicode letter, digit or underscore
Bob.*\b\кошка\bBob ate the кошка
\BNot a word boundaryc.*\Bcat\B.*copycats


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POSIX Classes

CharacterLegendExampleSample Match
[:alpha:]PCRE (C, PHP, R…): ASCII letters A-Z and a-z[8[:alpha:]]+WellDone88
[:alpha:]Ruby 2: Unicode letter or ideogram[[:alpha:]\d]+кошка99
[:alnum:]PCRE (C, PHP, R…): ASCII digits and letters A-Z and a-z[[:alnum:]]{10}ABCDE12345
[:alnum:]Ruby 2: Unicode digit, letter or ideogram[[:alnum:]]{10}кошка90210
[:punct:]PCRE (C, PHP, R…): ASCII punctuation mark[[:punct:]]+?!.,:;
[:punct:]Ruby: Unicode punctuation mark[[:punct:]]+‽,:〽⁆


(direct link)

Inline Modifiers

None of these are supported in JavaScript. In Ruby, beware of (?s) and (?m).
ModifierLegendExampleSample Match
(?i)Case-insensitive mode
(except JavaScript)
(?i)MondaymonDAY
(?s)DOTALL mode (except JS and Ruby). The dot (.) matches new line characters (\r\n). Also known as "single-line mode" because the dot treats the entire input as a single line(?s)From A.*to ZFrom A
to Z
(?m)Multiline mode
(except Ruby and JS) ^ and $ match at the beginning and end of every line
(?m)1\r\n^2$\r\n^3$1
2
3
(?m)In Ruby: the same as (?s) in other engines, i.e. DOTALL mode, i.e. dot matches line breaks(?m)From A.*to ZFrom A
to Z
(?x)Free-Spacing Mode mode
(except JavaScript). Also known as comment mode or whitespace mode
(?x) # this is a
# comment
abc # write on multiple
# lines
[ ]d # spaces must be
# in brackets
abc d
(?n).NET: named capture onlyTurns all (parentheses) into non-capture groups. To capture, use named groups.
(?d)Java: Unix linebreaks onlyThe dot and the ^ and $ anchors are only affected by \n


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Lookarounds

LookaroundLegendExampleSample Match
(?=…)Positive lookahead(?=\d{10})\d{5}01234 in 0123456789
(?<=…)Positive lookbehind(?<=\d)catcat in 1cat
(?!…)Negative lookahead(?!theatre)the\w+theme
(?<!…)Negative lookbehind\w{3}(?<!mon)sterMunster


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Character Class Operations

Class OperationLegendExampleSample Match
[…-[…]].NET: character class subtraction. One character that is in those on the left, but not in the subtracted class.[a-z-[aeiou]]Any lowercase consonant
[…-[…]].NET: character class subtraction.[\p{IsArabic}-[\D]]An Arabic character that is not a non-digit, i.e., an Arabic digit
[…&&[…]]Java, Ruby 2+: character class intersection. One character that is both in those on the left and in the && class.[\S&&[\D]]An non-whitespace character that is a non-digit.
[…&&[…]]Java, Ruby 2+: character class intersection.[\S&&[\D]&&[^a-zA-Z]]An non-whitespace character that a non-digit and not a letter.
[…&&[^…]]Java, Ruby 2+: character class subtraction is obtained by intersecting a class with a negated class[a-z&&[^aeiou]]An English lowercase letter that is not a vowel.
[…&&[^…]]Java, Ruby 2+: character class subtraction[\p{InArabic}&&[^\p{L}\p{N}]]An Arabic character that is not a letter or a number


(direct link)

Other Syntax

SyntaxLegendExampleSample Match
\KKeep Out
Perl, PCRE (C, PHP, R…), Python's alternate regex engine, Ruby 2+: drop everything that was matched so far from the overall match to be returned
prefix\K\d+12
\Q…\EPerl, PCRE (C, PHP, R…), Java: treat anything between the delimiters as a literal string. Useful to escape metacharacters.\Q(C++ ?)\E(C++ ?)




next
 The 1001 ways to use Regex




1-6 of 6 Threads
James
May 17, 2016 - 06:17
Subject: Valuable Resource

I've been using this site for years as a guide to remind me of the Regex syntax. It's the best I have found on the net. It doesn't have a bunch of useless clutter, but simply the information I need
Piotr – Kraków
February 14, 2016 - 05:31
Subject: Printable pdf

Hi guys! I've created printable pdf of the cheat sheet and versioned it under git. You can see it (and hopefully work with it) here:
https://github.com/palucki/regexcheatsheet
Regards, Piotr
Nora – Mexico
July 19, 2015 - 05:16
Subject: Thank you for an excellent resource

Thank you for taking the time to put together such a comprehensive and informative resource and share your knowledge of such a complex topic. It will be my go-to regex cheat sheet from now on!
tjpower – St. Louis MO.
July 11, 2015 - 02:30
Subject: Excellent

This page will definitely go in my favorites. I use regex a lot, but not enough to remember all the intricate tricks to retrieve some of the sophisticated patterns I've had to match, replace, or remove. Thanks for the cheat sheet.
Prasad Nutalapati – Chicago, IL
June 03, 2015 - 02:18
Subject: One single place for most of my regular expressions reference

I am a Java Programmer, but not a computer science graduate. I have no knowledge to start with when to code using regex parameters in Java coding. It was always an enigma for me. I used to just pass through the difficulty by googling. But one time, I could not find the suitable example. This is the one place that is invaluable for me. Even though the content can be improved with more explanation of each example that has been given, I can start to struggle/work with this site. The author deserves kudos and big thank you.
Prasad Nutalapati
Reply to Prasad Nutalapati
Rex
June 03, 2015 - 08:48
Subject: RE: One single place for most of my regular expressions reference

What a treat to read your message first thing in the morning, Prasad, thank you for your most kind encouragements. -Rex
Elena – Toronto
May 27, 2015 - 02:28
Subject: Thank you

Thank you so much, It is people like you who help make our world a better place


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