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 = /^([0-9a-f]{1,4}:)+(([0-9a-f]{1,4})?:)+([0-9a-f]{1,4})(?= )/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^([0-9a-f]{1,4}:)+(([0-9a-f]{1,4})?:)+([0-9a-f]{1,4})(?= )', 'gm') const str = `2a03:2880:30ff:4::face:b00c -- 2600:387:f:4533::8 - - 2600:387:5:805::84 - - 2a02:120b:2c12:df00:bc9f:adfd:eac6:4011 - - 2601:602:8b00:e50::c1f0 - - 2409:4042:112:8a7b::27bd:70b1 - - 2603:7000:a803:beb2:e0c0:3f:2a1b:5d60 - - ::1 - - :a:1 - - :bh:lh:1 - - 1:1:fEd1:1:abdc:1 - - ::ffff:192.0.2.128 - - 0000:0000:0000:0000:0000:0000:0000:0001 - - 2001:0db8:0000:0000:0000:ff00:0042:8329 - - 2001:db8:0:0:0:ff00:42:8329 - - 2001:db8::ff00:42:8329 - - 2001:0db8:0000:0000:0000:ff00:0042:8329 - - 2a03:2880:30ff:4::face:b00c -- 2600:387:f:4533::8 - - 2600:387:5:805::84 - - 2a02:120b:2c12:df00:bc9f:adfd:eac6:4011 - - 2600:387:0:80f::4a - - `; // 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