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

/
/
gi

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?i)([a-z]+|\d+[a-z]*|\([a-z0-9\s()+/*-]+?\))\s*(?:\*?\s*([a-z]+)|\*\s*(\d+[a-z]*)|\*?\s*(\([a-z0-9\s()+/*-]+?\)))\s*(\+|-)\s*(?:\1\s*(?:\*?\s*([a-z]+)|\*\s*(\d+[a-z]*)|\*?\s*(\([a-z0-9\s()+/*-]+?\)))|(?:([a-z]+)|(\d+[a-z]*)|(\([a-z0-9\s()+/*-]+?\)))\s*\*\s*\1)|(?:([a-z]+)|\*\s*(\d+[a-z]*)|\*?\s*(\([a-z0-9\s()+/*-]+?\)))\s*\*\s*([a-z]+|\d+[a-z]*|\([a-z0-9\s()+/*-]+?\))\s*(\+|-)\s*(?:\15\s*(?:\*?\s*([a-z]+)|\*\s*(\d+[a-z]*)|\*?\s*(\([a-z0-9\s()+/*-]+?\)))|(?:([a-z]+)|(\d+[a-z]*)|(\([a-z0-9\s()+/*-]+?\)))\s*\*\s*\15)`) var str = `Can be used to simplify a bit calculs as "2y - z * 2" or (4-z) (x/3 * 4) - (4-z)(1 / xy).` var substitution = "$1$15($2$3$4$12$13$14 $5 $6$7$8$9$10$11$16$17$18$19$20$21$22)" fmt.Println(re.ReplaceAllString(str, substitution)) }

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/