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

/
/
gmi

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /^(?:https?:\/\/)?(?:(?:www\.)?youtube\.com\/(?:(?:v\/)|(?:embed\/|watch(?:\/|\?)){1,2}(?:.*v=)?|.*v=)?|(?:www\.)?youtu\.be\/)([A-Za-z0-9_\-]+)&?.*$/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?:https?:\\\/\\\/)?(?:(?:www\\.)?youtube\\.com\\\/(?:(?:v\\\/)|(?:embed\\\/|watch(?:\\\/|\\?)){1,2}(?:.*v=)?|.*v=)?|(?:www\\.)?youtu\\.be\\\/)([A-Za-z0-9_\\-]+)&?.*$', 'gmi') const str = `http://www.youtube.com/watch/iwGFalTRHDA http://www.youtube.com/v/iwGFalTRHDA http://www.youtube.com/v/i_GFalTRHDA http://www.youtube.com/watch?v=i-GFalTRHDA&feature=related http://www.youtube.com/attribution_link?u=/watch?v=aGmiw_rrNxk&feature=share&a=9QlmP1yvjcllp0h3l0NwuA http://www.youtube.com/attribution_link?a=fF1CWYwxCQ4&u=/watch?v=qYr8opTPSaQ&feature=em-uploademail http://www.youtube.com/attribution_link?a=fF1CWYwxCQ4&feature=em-uploademail&u=/watch?v=qYr8opTPSaQ http://www.youtube.com/watch?v=iwGFalTRHDA https://www.youtube.com/watch?v=iwGFalTRHDA http://www.youtube.com/watch?v=iwGFalTRHDA&feature=related http://youtu.be/iwGFalTRHDA http://www.youtube.com/embed/watch?feature=player_embedded&v=iwGFalTRHDA http://www.youtube.com/embed/watch?v=iwGFalTRHDA http://www.youtube.com/embed/v=iwGFalTRHDA http://www.youtube.com/watch?feature=player_embedded&v=iwGFalTRHDA http://www.youtube.com/watch?v=iwGFalTRHDA www.youtube.com/watch?v=iwGFalTRHDA www.youtu.be/iwGFalTRHDA youtu.be/iwGFalTRHDA youtube.com/watch?v=iwGFalTRHDA `; const subst = ``; // 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