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

/
/
gmi

Test String

Code Generator

Language

Generated Code

const regex = /(^127\.0\.0\.1[\s]+|^0\.0\.0\.0[\s]+)([0-9a-z_.-]+$)|^([0-9a-z_.-]+$)/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('(^127\\.0\\.0\\.1[\\s]+|^0\\.0\\.0\\.0[\\s]+)([0-9a-z_.-]+$)|^([0-9a-z_.-]+$)', 'gmi') const str = `# hpHosts - FSA only # # The following are hosts in the hpHosts database with the FSA classification ONLY. # 127.0.0.1 localhost #IPv4 localhost 127.0.0.1 localhost ::1 localhost #IPv6 localhost # # BAD SITES START HERE # 0.0.0.0 very#badexample.com very#badexample.com domain@with.com doma\$in AuThedMine.cOm domain.0cf 127.0.0.1 0-0-----------------------------------------------------------0.com 127.0.0.1 0-google.com 127.0.0.1 00-lawyer.com 127.0.0.1 0000.support 0.01.2.13.3.sydneypropertyinvestors.com 0.01.2.23.3.sydneypropertyinvestors.com 000.9.009.09.ekurbani.com 000.9.019.09.ekurbani.com 000000-0.000webhostapp.com 00004563.000webhostapp.com 000m8ih.wcomhost.com 000m8n1.wcomhost.com 000m8pk.wcomhost.com 000m9w3.wcomhost.com 000macu.wcomhost.com 000magu.wcomhost.com 000map9.wcomhost.com 000may2.wcomhost.com 000mhl7.wcomhost.com 000mhpe.wcomhost.com 000mhpg.wcomhost.com 1xbet86.com 1xbet87.com 1xbet90.com 1xbet31.com 1xbet46.com 1xbet28.com 1xbet35.com 1xbet49.com nejakyhost.cz 0.0.0.0 cnhv.co 0.0.0.0 coin-hive.com 0.0.0.0 coinhive.com 0.0.0.0 authedmine.com 0.0.0.0 api.jsecoin.com 0.0.0.0 load.jsecoin.com 0.0.0.0 server.jsecoin.com 0.0.0.0 miner.pr0gramm.com 0.0.0.0 minemytraffic.com 0.0.0.0 crypto-loot.com 0.0.0.0 cryptaloot.pro 0.0.0.0 cryptoloot.pro 0.0.0.0 coinerra.com 0.0.0.0 coin-have.com 0.0.0.0 minero.pw 0.0.0.0 minero-proxy-01.now.sh 0.0.0.0 minero-proxy-02.now.sh 0.0.0.0 minero-proxy-03.now.sh 0.0.0.0 api.inwemo.c 127.0.0.1 sfdfsdfsdfsdfsd pool.pebblemedia.adhese.com`; // 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