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

/
/
img

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /<img([^>]*)src="[(([^:"]*)({png|gif|jpg|jpeg}))]"/img; // Alternative syntax using RegExp constructor // const regex = new RegExp('<img([^>]*)src="[(([^:"]*)({png|gif|jpg|jpeg}))]"', 'img') const str = `<!DOCTYPE html> <html> <body> <img src="smiley.gif" alt="Smiley face" height="42" width="42" style="float:right"> <p>Insert an image from another folder:</p> <img src="/images/stickman.gif" alt="Stickman" width="24" height="39"> <p style="float:left">Insert an image from a web site:</p> <img style="color:green; float:right;" src="http://www.w3schools.com/images/lamp.gif" alt="Lamp" width="15" height="15"> </body> </html> `; const subst = `<img \2`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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