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 (14)

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

/
/
ix

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /\b( # MAC address like xx:xx:xx:xx:xx:xx [0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2} | # MAC address like xx-xx-xx-xx-xx-xx [0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2} | # MAC address like xxxx.xxxx.xxxx [0-9a-f]{4}\.[0-9a-f]{4}\.[0-9a-f]{4} | # IPv4 address in dotted-quad format # Not a lot of value for our needs in checking range of each octet # Need to be more mindful of performance here anyway. \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3} )\b/i; // Alternative syntax using RegExp constructor // const regex = new RegExp('\\b( # MAC address like xx:xx:xx:xx:xx:xx [0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2} | # MAC address like xx-xx-xx-xx-xx-xx [0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2}-[0-9a-f]{2} | # MAC address like xxxx.xxxx.xxxx [0-9a-f]{4}\\.[0-9a-f]{4}\\.[0-9a-f]{4} | # IPv4 address in dotted-quad format # Not a lot of value for our needs in checking range of each octet # Need to be more mindful of performance here anyway. \\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3} )\\b', 'i') const str = `192.168.1.2 10.0.0.0 ff:ff:ff:ff:ff:ff FF-FF-FF-FF-FF-FF FFFF.FFFF.FFFF ffff.ffff.ffff blah127.0.0.1haha foo127.0.0.1 `; const subst = `\1`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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 JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions