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

/
/
g

Test String

Code Generator

Language

Generated Code

const regex = / *(?:.*\S.*\n)+\n? *: +(?:.|\n)+?(?:\n{2,}(?=\S)(?! *: +)(?! *(?:\S.*\n)+?\n? *: +)|$)/g; // Alternative syntax using RegExp constructor // const regex = new RegExp(' *(?:.*\\S.*\\n)+\\n? *: +(?:.|\\n)+?(?:\\n{2,}(?=\\S)(?! *: +)(?! *(?:\\S.*\\n)+?\\n? *: +)|$)', 'g') const str = `=== Single <dt> and <dd> GitHub : a site where over 73 million developers shape the future of software, together === Multiple <dt>-<dd> group Firefox : a free, open source, cross-platform, graphical web browser developed by the Mozilla Corporation and hundreds of volunteers MDN : provides information about Open Web technologies including HTML, CSS, and APIs for both Web sites and progressive web apps === Single <dt> with multiple <dd>s Apple : an American multinational technology company that specializes in consumer electronics, computer software and online services. : an edible fruit produced by an apple tree === Multiple <dt>s Windows Microsoft Windows Win : a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft === separated by blank lines Solaris : a 1961 science fiction novel by Polish writer Stanisław Lem : a proprietary Unix operating system originally developed by Sun Microsystems === <dd>s with inline breaks Oracle : an American multinational computer technology corporation headquartered in Austin, Texas : the priest or priestess uttering the prediction, may also refer to the site of the oracle === 😂 : 😂 face with tears of joy === Term 1 : This is a definition with two paragraphs. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus. Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus. : Second definition for term 1, also wrapped in a paragraph because of the blank line preceding it. Term 2 : This definition has a code block, a blockquote and a list. code block. > block quote > on two lines. 1. first list item 2. second list item`; 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