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 = /(?P<client_ip>[\d.]+) - - \[(?P<timestamp>.*?)\] "(?P<request_method>\w+) (?P<request_uri>.*?) (?P<protocol>.*?) (?P<protocol_version>.*?)" (?P<status>\d+) (?P<response_size>\d+|-) "(?P<referrer>.*?)" "(?P<user_agent>.*?)"/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?P<client_ip>[\\d.]+) - - \\[(?P<timestamp>.*?)\\] "(?P<request_method>\\w+) (?P<request_uri>.*?) (?P<protocol>.*?) (?P<protocol_version>.*?)" (?P<status>\\d+) (?P<response_size>\\d+|-) "(?P<referrer>.*?)" "(?P<user_agent>.*?)"', 'gm') const str = `209.160.24.63 - - [28/Mar/2023:18:22:16] "GET /product.screen?productId=WC-SH-A02&JSESSIONID=SD0SL6FF7ADFF4953 HTTP 1.1" 200 3878 "http://www.google.com" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.46 Safari/536.5" 349 209.160.24.63 - - [28/Mar/2023:18:22:16] "POST /oldlink?itemId=EST-6&JSESSIONID=SD0SL6FF7ADFF4953 HTTP 1.1" 200 1748 "http://www.buttercupgames.com/oldlink?itemId=EST-6" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.46 Safari/536.5" 731 `; // 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