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

/
/
usigmUJ

Test String

Code Generator

Language

Generated Code

const regex = /^(?:[\+-]?\d{4}(?!\d{2}\b))(?:(-?)(?:(?:0[1-9]|1[0-2])(?:\1(?:[12]\d|0[1-9]|3[01]))?|W(?:[0-4]\d|5[0-2])(?:-?[1-7])?|(?:00[1-9]|0[1-9]\d|[12]\d{2}|3(?:[0-5]\d|6[1-6])))(?:[T\s](?:(?:(?:[01]\d|2[0-3])(?:(:?)[0-5]\d)?|24\:?00)(?:[\.,]\d+(?!:))?)?(?:\2[0-5]\d(?:[\.,]\d+)?)?(?:[zZ]|(?:[\+-])(?:[01]\d|2[0-3]):?(?:[0-5]\d)?)?)?)?$/usigm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?:[\\+-]?\\d{4}(?!\\d{2}\\b))(?:(-?)(?:(?:0[1-9]|1[0-2])(?:\\1(?:[12]\\d|0[1-9]|3[01]))?|W(?:[0-4]\\d|5[0-2])(?:-?[1-7])?|(?:00[1-9]|0[1-9]\\d|[12]\\d{2}|3(?:[0-5]\\d|6[1-6])))(?:[T\\s](?:(?:(?:[01]\\d|2[0-3])(?:(:?)[0-5]\\d)?|24\\:?00)(?:[\\.,]\\d+(?!:))?)?(?:\\2[0-5]\\d(?:[\\.,]\\d+)?)?(?:[zZ]|(?:[\\+-])(?:[01]\\d|2[0-3]):?(?:[0-5]\\d)?)?)?)?$', 'usigm') const str = `2021 2021-10 2021-00 2021-13 2021-10-24 2021-10-00 2021-10-32 2021-10-24T10 2021-10-24T48 2021-10-24T10:30 2021-10-24T10:95 2021-10-24T10:30:47 2021-10-24T10:30:78 2021-10-24T10:30:47.5 2021-10-24T10:30:47.333 2021-10-24T10:30:47.333333 2021-10-24T10:30:47Z 2021-10-24T10:30:78Z 2021-10-24T10:30:47.5Z 2021-10-24T10:30:47.333Z 2021-10-24T10:30:47.333333Z 2021-10-24T10:30:47-03:00 2021-10-24T10:30:78-03:00 2021-10-24T10:30:47.5-03:00 2021-10-24T10:30:47.333-03:00 2021-10-24T10:30:47.333333-03:00 Nate☬158⚈̥̥̥̥̥̀ᴗ✯`; // 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