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
  • 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[0-4]\d|25[0-5]|1\d{2}|[1-9]?\d)\.){3}(?:2[0-4]\d|25[0-5]|1\d{2}|[1-9]?\d)$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?:(?:2[0-4]\\d|25[0-5]|1\\d{2}|[1-9]?\\d)\\.){3}(?:2[0-4]\\d|25[0-5]|1\\d{2}|[1-9]?\\d)$', 'gm') const str = `validates: 192.68.35.35 0.0.0.0 255.0.0.0 192.168.1.0 192.168.0.1 255.255.255.0 1.1.1.1 255.255.255.255 249.249.249.249 200.200.200.200 199.199.199.199 100.100.100.100 99.99.99.99 0.0.0.0 9.9.9.9 10.10.10.10 99.99.99.99 100.100.100.100 109.109.109.109 110.110.110.110 199.199.199.199 200.200.200.200 249.249.249.249 250.250.250.250 255.255.255.255 should not validate: 256.256.256.260 192.168.0.0/24 192.168..1 192.168.1 1 1. 1.1 1.1. 1.1.1 1.1.1. 1.1.1.1. 1.1.1.1.1 .1.1.1 01.01.01.01 09.09.09.09 1.0.0.1.0 010.1.1.1 123456 123123123123 .127.0.0.1`; // 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