Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
g

Test String

Code Generator

Language

Generated Code

$re = '/(\w)(?=\1)/'; $str = '5228833336355848549915459366737982598312959583817455621545976784792489468198365998232722734876612332352376192813552949814275947575774339529811976644361517795586998319242241614813622734255797569571577699238592667287428166398221572885869416419682687759743978434571821267146514338394624525648338739929479912368172669885577319718389278168766844487948761697438722556857882433224393723131298876252626643517236883999115665656935521675772866516185899317132494716723615493476397115627687887665194781746377341468995954554518252916859227397693885254329628812355612487594445522395853551734567498838382248616137969637971369615443599973588326388792893969924855316437952313492551671545714262784738343517166544197194547173515155927244175447296474282154114951181648317875827525814453758846194548872789943372281952995222779173812444186491115426476188672253249744478946863317915136832199132868917891243591195719354721129116229164688256853628339233919671468781913167415624214152793864585332944468428849171876873433621524242289488135675313544498245498637424139153782925723745249728743885493877792648576673196889949568317234125863369187953788611841388353999875519172896329524346527265231767868839696693328273381772726782949166112932954356923757485139367298699922984925977724972944277991686823219295939734313874834861796179591659174726432357533113896212781566659154939419866797488347448551719481632572231632463575591599696388223344219228325134233238538854289437756331848887242423387542214691157226725179683638967415678697625138177633444765126223885478348951332634398291612134852858683942466178329922655822225426534359191696177633167962839847985826676955417426617126288255366123169174674348417932158291334646767637764323226842771523598562429399935789788215958367362467652444854123951972118358417629679454978687337137675495295768451719631999398617828287671937584998697959425845883145736323818225129311845997214987663433375689621746665629187252511643969315283316269222835744532431378945137649959158495714472963839397214332815241141327714672141875129895'; preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0); // Print the entire match result var_dump($matches);

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php