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

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?:https?:\/\/)?(?:www\.)?(?:youtu\.be\/|youtube\.com\/(?:embed\/|v\/|playlist\?|watch\?v=|watch\?.+(?:&|&#38;);v=))([a-zA-Z0-9\-_]{11})?(?:(?:\?|&|&#38;)index=((?:\d){1,3}))?(?:(?:\?|&|&#38;)?list=([a-zA-Z\-_0-9]{34}))?(?:\S+)?`) var str = `https://www.youtube.com/playlist?list=PL1eC1aP-LYNg2ya1ywPj0pipd0y2EWGEl https://www.youtube.com/watch?v=4UcfECYbDYQ&index=1&list=PL1eC1aP-LYNg2ya1ywPj0pipd0y2EWGEl https://youtu.be/4UcfECYbDYQ?list=PL1eC1aP-LYNg2ya1ywPj0pipd0y2EWGEl https://www.youtube.com/watch?v=Svmor6ouuO4&index=4&list=PL1eC1aP-LYNg2ya1ywPj0pipd0y2EWGEl https://www.youtube.com/watch?v=M44e92KoIaE https://youtu.be/M44e92KoIaE https://www.youtube.com/embed/videoseries?list=PL1eC1aP-LYNg2ya1ywPj0pipd0y2EWGEl` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

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 Golang, please visit: https://golang.org/pkg/regexp/