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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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 = '/(?<code1>id="question-summary-)(?<code2>\d+)/'; $str = '<div class="question-summary" id="question-summary-80407"> <div class="statscontainer"> <div class="statsarrow"></div> <div class="stats"> <div class="vote"> <div class="votes"> <span class="vote-count-post "><strong>2</strong></span> <div class="viewcount">votes</div> </div> </div> <div class="status answered"> <strong>1</strong>answer </div> </div> <div class="views " title="60 views"> 60 views </div> </div> <div class="summary"> <h3><a href="/questions/80407/about-power-supply-of-opertional-amplifier" class="question-hyperlink">about power supply of opertional amplifier</a></h3> <div class="excerpt"> I am constructing an operational amplifier as shown in the following figure. I use a batter as supplier for the OP Amp and set it up as a non-inverting amp circuit. I saw that the output was clipped ... </div> <div class="tags t-op-amp"> <a href="/questions/tagged/op-amp" class="post-tag" title="show questions tagged \'op-amp\'" rel="tag">op-amp</a> </div> <div class="started fr"> <div class="user-info "> <div class="user-action-time"> asked <span title="2013-08-27 21:49:14Z" class="relativetime">11 hours ago</span> </div> <div class="user-gravatar32"> <a href="/users/17060/user1285419"><div class=""><img src="https://www.gravatar.com/avatar/08ee68b20a4eceff26f7eee99b708c08?s=32&d=identicon&r=PG" alt="" width="32" height="32"></div></a> </div> <div class="user-details"> <a href="/users/17060/user1285419">user1285419</a><br> <span class="reputation-score" title="reputation score" dir="ltr">165</span><span title="5 bronze badges"><span class="badge3"></span><span class="badgecount">5</span></span> </div> </div> </div> </div> </div> <div class="question-summary" id="question-summary-80405"> <div class="statscontainer"> <div class="statsarrow"></div> <div class="stats"> <div class="vote"> <div class="votes"> <span class="vote-count-post "><strong>4</strong></span> <div class="viewcount">votes</div> </div> </div> <div class="status answered-accepted"> <strong>2</strong>answers </div> </div> <div class="views " title="64 views"> 64 views </div> </div> <div class="summary"> <h3><a href="/questions/80405/5v-regulator-power-dissipation" class="question-hyperlink">5V Regulator Power Dissipation</a></h3> <div class="excerpt"> I am using a 5V regulator (LP2950) from ON Semiconductor. I am using this for USB power and I\'m feeding in 9V from an adapter. USB requires maximum of 500mA right? So the maximum power dissipation in ... </div> <div class="tags t-voltage-regulator t-surface-mount t-heatsink t-5v t-power-dissipation"> <a href="/questions/tagged/voltage-regulator" class="post-tag" title="show questions tagged \'voltage-regulator\'" rel="tag">voltage-regulator</a> <a href="/questions/tagged/surface-mount" class="post-tag" title="show questions tagged \'surface-mount\'" rel="tag">surface-mount</a> <a href="/questions/tagged/heatsink" class="post-tag" title="show questions tagged \'heatsink\'" rel="tag">heatsink</a> <a href="/questions/tagged/5v" class="post-tag" title="show questions tagged \'5v\'" rel="tag">5v</a> <a href="/questions/tagged/power-dissipation" class="post-tag" title="show questions tagged \'power-dissipation\'" rel="tag">power-dissipation</a> </div> <div class="started fr"> <div class="user-info "> <div class="user-action-time"> asked <span title="2013-08-27 21:39:31Z" class="relativetime">11 hours ago</span> </div> <div class="user-gravatar32"> <a href="/users/10082/david-norman"><div class=""><img src="https://www.gravatar.com/avatar/8b073417e471077280b3fc5ff2eaf1f7?s=32&d=identicon&r=PG" alt="" width="32" height="32"></div></a> </div> <div class="user-details"> <a href="/users/10082/david-norman">David Norman</a><br> <span class="reputation-score" title="reputation score" dir="ltr">322</span><span title="3 silver badges"><span class="badge2"></span><span class="badgecount">3</span></span><span title="10 bronze badges"><span class="badge3"></span><span class="badgecount">10</span></span> </div> </div> </div> </div> </div>'; 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