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

/
/
g

Test String

Code Generator

Language

Generated Code

const regex = /&lt;iframe.*?src="(?![^"]*(?:youtube|vimeo|soundcloud)).*?&lt;\/iframe&gt;/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('&lt;iframe.*?src="(?![^"]*(?:youtube|vimeo|soundcloud)).*?&lt;\\\/iframe&gt;', 'g') const str = `&lt;p&gt;&lt;iframe src="http://www.3you3tube.com/embed/YoX1yc92MOU" width="500" height="300" frameborder="0" scrolling="auto"&gt;&lt;/iframe&gt;&lt;/p&gt; 29 &lt;p&gt;text daily to place domain staff as volunteers with charity partners, we know all too well that the "V" word can sometimes be misunderstood. Occasionally seen as a dusty, worthy word, it can conjure images of coffee mornings and bric-a-brac stalls. So its not always as easy as you might think to get people to embrace their inner-volunteer. That's why the &lt;a href="http://www.domain.co.uk/sdfn/2010/11/connect-create-domain-volunteers.shtml"&gt;Conne&lt;p&gt;&lt;iframe src="http://www.youtube.com/embed/YoX1yc92MOU" width="500" height="300" frameborder="0" scrolling="auto"&gt;&lt;/iframe&gt;&lt;/p&gt;`; // 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