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

/
/
g

Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(?<code1>id=""question-summary-)(?<code2>\d+)"; string input = @"<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>"; foreach (Match m in Regex.Matches(input, pattern)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx