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 = /^([a-zA-Z0-9!#$%&'*+\/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+\/=?^_`{|}~-]+)*@(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?\.)+[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?)$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^([a-zA-Z0-9!#$%&\'*+\\\/=?^_`{|}~-]+(?:\\.[a-zA-Z0-9!#$%&\'*+\\\/=?^_`{|}~-]+)*@(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?\\.)+[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?)$', 'gm') const str = `--------- valid --------- something@something.com someone@localhost.localdomain someone@127.0.0.1 a@b.b a/b@domain.com {}@domain.com m*'!%@something.sa tu!!7n7.ad##0!!!@company.ca %@com.com !#\$%&'*+/=?^_\`{|}~.-@com.com USER@EXAMPLE.COM someone@do-ma-in.com a@p.com -------- invalid -------- somebody@example a@p.com .wooly@example.com wo..oly@example.com invalid:email@example.com @somewhere.com example.com @@example.com a space@example.com something@ex..ample.com a\\b@c ----- empty string ---- -------- space -------- someone@somewhere.com. \\"\\"test\\blah\\"\\"@example.com \\"testblah\\"@example.com someone@somewhere.com@ someone@somewhere_com someone@some:where.com . F/s/f/a@feo+re.com some+long+email+address@some+host-weird-/looking.com a @p.com a\\u0020@p.com a\\u0009@p.com a\\u000B@p.com a\\u000C@p.com a\\u2003@p.com a\\u3000@p.com ddjk-s-jk@asl-.com someone@do-.com somebody@-p.com somebody@-.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