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

r"
"
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)<hi>((.|\n)*?)</hi>`) var str = `<hi> Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aenean tincidunt diam sit amet semper vestibulum. Donec dictum dapibus magna vitae pharetra. Fusce condimentum velit at tempus aliquam. Maecenas maximus scelerisque nisi, et gravida felis molestie quis. Nunc nec mauris in ligula imperdiet rhoncus. Donec dignissim magna eu consectetur luctus. Phasellus sed massa vitae nisl congue congue. Etiam nec luctus dolor, eget placerat ligula. Fusce mollis neque vitae fermentum gravida. Suspendisse maximus felis risus, vel fringilla mauris tristique quis. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Interdum et malesuada fames ac ante ipsum primis in faucibum </hi> Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aenean tincidunt diam sit amet semper vestibulum. Donec dictum dapibus magna vitae pharetra. Fusce condimentum velit at tempus aliquam. Maecenas maximus scelerisque nisi, et gravida felis molestie quis. Nunc nec mauris in ligula imperdiet rhoncus. Donec dignissim magna eu consectetur luctus. Phasellus sed massa vitae nisl congue congue. Etiam nec luctus dolor, eget placerat ligula. Fusce mollis neque vitae fermentum gravida. Suspendisse maximus felis risus, vel fringilla mauris tristique quis. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Interdum et malesuada fames ac ante ipsum primis in faucibus. <hi> Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aenean tincidunt diam sit amet semper vestibulum. Donec dictum dapibus magna vitae pharetra. Fusce condimentum velit at tempus aliquam. Maecenas maximus scelerisque nisi, et gravida felis molestie quis. Nunc nec mauris in ligula imperdiet rhoncus. Donec dignissim magna eu consectetur luctus. Phasellus sed massa vitae nisl congue congue. Etiam nec luctus dolor, eget placerat ligula. Fusce mollis neque vitae fermentum gravida. Suspendisse maximus felis risus, vel fringilla mauris tristique quis. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Interdum et malesuada fames ac ante ipsum primis in faucibum </hi>` 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/