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 = /^\s*((((([0-9A-Fa-f]{1,4})|\*):){7}((([0-9A-Fa-f]{1,4})|\*)|:))|(((([0-9A-Fa-f]{1,4})|\*):){6}(:(([0-9A-Fa-f]{1,4})|\*)|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(((([0-9A-Fa-f]{1,4})|\*):){5}(((:(([0-9A-Fa-f]{1,4})|\*)){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(((([0-9A-Fa-f]{1,4})|\*):){4}(((:(([0-9A-Fa-f]{1,4})|\*)){1,3})|((:(([0-9A-Fa-f]{1,4})|\*))?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\*):){3}(((:(([0-9A-Fa-f]{1,4})|\*)){1,4})|((:(([0-9A-Fa-f]{1,4})|\*)){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\*):){2}(((:(([0-9A-Fa-f]{1,4})|\*)){1,5})|((:(([0-9A-Fa-f]{1,4})|\*)){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\*):){1}(((:(([0-9A-Fa-f]{1,4})|\*)){1,6})|((:(([0-9A-Fa-f]{1,4})|\*)){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:(([0-9A-Fa-f]{1,4})|\*)){1,7})|((:(([0-9A-Fa-f]{1,4})|\*)){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))\s*$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\s*((((([0-9A-Fa-f]{1,4})|\\*):){7}((([0-9A-Fa-f]{1,4})|\\*)|:))|(((([0-9A-Fa-f]{1,4})|\\*):){6}(:(([0-9A-Fa-f]{1,4})|\\*)|((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(((([0-9A-Fa-f]{1,4})|\\*):){5}(((:(([0-9A-Fa-f]{1,4})|\\*)){1,2})|:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(((([0-9A-Fa-f]{1,4})|\\*):){4}(((:(([0-9A-Fa-f]{1,4})|\\*)){1,3})|((:(([0-9A-Fa-f]{1,4})|\\*))?:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\\*):){3}(((:(([0-9A-Fa-f]{1,4})|\\*)){1,4})|((:(([0-9A-Fa-f]{1,4})|\\*)){0,2}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\\*):){2}(((:(([0-9A-Fa-f]{1,4})|\\*)){1,5})|((:(([0-9A-Fa-f]{1,4})|\\*)){0,3}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(((([0-9A-Fa-f]{1,4})|\\*):){1}(((:(([0-9A-Fa-f]{1,4})|\\*)){1,6})|((:(([0-9A-Fa-f]{1,4})|\\*)){0,4}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(:(((:(([0-9A-Fa-f]{1,4})|\\*)){1,7})|((:(([0-9A-Fa-f]{1,4})|\\*)){0,5}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:)))\\s*$', 'gm') const str = `2404:6800:4003:c02::8a 2404:6800:4003:804::200e 2001:4998:c:a06::2:4008 fe80::21d8:f50:c295:c4be 2001:cdba::e:9652 2001:cdba:0:0:0:0:3257:9652 2001:cdba::3257:9652 2001:cdba::1222 21DA:D3:0:2F3B:2AA:FF:FE28:9C5A 2001:cdba::1:2:3:3257:9652 2404::4003:804::200e 1234:Fd2:2:1:89::4500 1234:Fd2:12:1:89::4500 2001:DB8:0:0:0:0:0:* 2001:DB8:0:0:0:*:*:* 2001:DB8::0:* 2001:DB8:0:0:0:*:0:1 :: 2001:DB8:0:0:0:* 2001:*: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