Regular Expressions 101

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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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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 = /^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?P<major>0|[1-9]\\d*)\\.(?P<minor>0|[1-9]\\d*)\\.(?P<patch>0|[1-9]\\d*)(?:-(?P<prerelease>(?:0|[1-9]\\d*|\\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\\.(?:0|[1-9]\\d*|\\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?$', 'gm') const str = `Valid Semantic Versions Source: https://semver.org 0.0.4 1.2.3 10.20.30 1.1.2-prerelease+meta 1.1.2+meta 1.1.2+meta-valid 1.0.0-alpha 1.0.0-beta 1.0.0-alpha.beta 1.0.0-alpha.beta.1 1.0.0-alpha.1 1.0.0-alpha0.valid 1.0.0-alpha.0valid 1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay 1.0.0-rc.1+build.1 2.0.0-rc.1+build.123 1.2.3-beta 10.2.3-DEV-SNAPSHOT 1.2.3-SNAPSHOT-123 1.0.0 2.0.0 1.1.7 2.0.0+build.1848 2.0.1-alpha.1227 1.0.0-alpha+beta 1.2.3----RC-SNAPSHOT.12.9.1--.12+788 1.2.3----R-S.12.9.1--.12+meta 1.2.3----RC-SNAPSHOT.12.9.1--.12 1.0.0+0.build.1-rc.10000aaa-kk-0.1 99999999999999999999999.999999999999999999.99999999999999999 1.0.0-0A.is.legal Invalid Semantic Versions 1 1.2 1.2.3-0123 1.2.3-0123.0123 1.1.2+.123 +invalid -invalid -invalid+invalid -invalid.01 alpha alpha.beta alpha.beta.1 alpha.1 alpha+beta alpha_beta alpha. alpha.. beta 1.0.0-alpha_beta -alpha. 1.0.0-alpha.. 1.0.0-alpha..1 1.0.0-alpha...1 1.0.0-alpha....1 1.0.0-alpha.....1 1.0.0-alpha......1 1.0.0-alpha.......1 01.1.1 1.01.1 1.1.01 1.2 1.2.3.DEV 1.2-SNAPSHOT 1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788 1.2-RC-SNAPSHOT -1.0.3-gamma+b7718 +justmeta 9.8.7+meta+meta 9.8.7-whatever+meta+meta 99999999999999999999999.999999999999999999.99999999999999999----RC-SNAPSHOT.12.09.1--------------------------------..12`; // 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