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

/
/
gm

Test String

Code Generator

Language

Generated Code

const regex = /^(?!.*\-{2}.*)(?!.*\+{2}.*)(?!.*\.{2}.*)(?P<major>(?!0)(\d*)|([0[^\d]))((?>\.)(?P<minor>\g<1>))\.(?P<patch>\g<minor>)(?![\+\-][^a-zA-Z0-9])(\g<2>(\-(?P<release>[a-zA-Z0-9\.-]+)))?(\+(?P<build>\g<9>))?$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?!.*\\-{2}.*)(?!.*\\+{2}.*)(?!.*\\.{2}.*)(?P<major>(?!0)(\\d*)|([0[^\\d]))((?>\\.)(?P<minor>\\g<1>))\\.(?P<patch>\\g<minor>)(?![\\+\\-][^a-zA-Z0-9])(\\g<2>(\\-(?P<release>[a-zA-Z0-9\\.-]+)))?(\\+(?P<build>\\g<9>))?$', 'gm') const str = `#good 0.1.2 1.2.3 10.20.3 1.2.3-alpha.23-pre 12.12.3-123.hexagon+dontmakemecompileplea.se 1.2.3-alpha-dev.51-something+mybuild-1-4-1975-clang 4.3.22+mybuild 4.1.405+hexa.13331-objectfiles # bad 01.2.3 1.02.3 2.3.04 a.1.1 1.a.1 1.1.a 1.2.3-rele..ase+build 1.2.3-release-something+..build 1.2.3-rele--ase+build 1.2.3-release-something+--build 1.2.3-release++build 1.2.3+-release-something-build`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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