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

/
/

Test String

Code Generator

Language

Generated Code

const regex = /(\d+\.\d+\.\d+\.\d+) ([a-zA-z0-9-]) ([a-zA-z0-9-]) (\[\d{2}\/\w{3}\/\d{4}:\d{2}:\d{2}:\d{2} -\d{4}\]) "(GET [\/a-zA-Z0-9.-]+ HTTP\/1.1)" \d{3} \d* "([a-zA-z0-9-])" "([a-zA-z0-9\/. ;+\\():]+)" "([a-zA-z0-9-])"/; // Alternative syntax using RegExp constructor // const regex = new RegExp('(\\d+\\.\\d+\\.\\d+\\.\\d+) ([a-zA-z0-9-]) ([a-zA-z0-9-]) (\\[\\d{2}\\\/\\w{3}\\\/\\d{4}:\\d{2}:\\d{2}:\\d{2} -\\d{4}\\]) "(GET [\\\/a-zA-Z0-9.-]+ HTTP\\\/1.1)" \\d{3} \\d* "([a-zA-z0-9-])" "([a-zA-z0-9\\\/. ;+\\\\():]+)" "([a-zA-z0-9-])"', '') const str = `66.249.69.58 - - [20/Nov/2015:03:54:09 -0500] "GET /robots.txt HTTP/1.1" 404 3652 "-" "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)" "-" `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; if ((m = regex.exec(str)) !== null) { // 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