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

/
/
gims

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?<=(?:\\[embed\\])|(?:\\[embed\\]\\s)|(?:))(https?:\\/\\/)(:?www\\.)?(:?youtube\\.com\\/watch|youtu\\.be\\/)([\\w\\?=\\&]+)(?=(?:\\[\\/embed\\])|(?:\\s\\[\\/embed\\])|(?:))"; final String string = "bla https://www.youtube.com/watch?v=Vpg9yizPP_g\n" + "http://www.youtube.com/watch?v=Vpg9yizPP_g bla\n" + "[embed]https://www.youtube.com/watch?v=Vpg9yizPP_g[/embed] bla\n" + "[embed] https://www.youtube.com/watch?v=Vpg9yizPP_g [/embed]\n" + "[embed]http://www.youtube.com/watch?v=Vpg9yizPP_g[/embed]\n" + "[embed] http://www.youtube.com/watch?v=Vpg9yizPP_g [/embed]\n" + "bla https://youtube.com/watch?v=Vpg9yizPP_g bla\n" + "http://youtube.com/watch?v=Vpg9yizPP_g\n" + "[embed]https://youtube.com/watch?v=Vpg9yizPP_g[/embed]bla\n" + "bla[embed] https://youtube.com/watch?v=Vpg9yizPP_g [/embed]\n" + "[embed]http://youtube.com/watch?v=Vpg9yizPP_g[/embed]\n" + "[embed] http://youtube.com/watch?v=Vpg9yizPP_g [/embed]\n" + "https://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g\n" + "http://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g\n" + "[embed]https://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g[/embed]\n" + "[embed] https://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g [/embed]\n" + "[embed]http://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g[/embed]\n" + "bla[embed] http://www.youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g [/embed]bla\n" + "https://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g bla\n" + "bla http://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g\n" + "[embed]https://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g[/embed]\n" + "[embed] https://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g [/embed]\n" + "[embed]http://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g[/embed]\n" + "[embed] http://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g [/embed]\n" + "https://youtu.be/Vpg9yizPP_g\n" + "http://youtu.be/Vpg9yizPP_g bla\n" + "[embed]https://youtu.be/Vpg9yizPP_g[/embed]\n" + "[embed] https://youtu.be/Vpg9yizPP_g [/embed]\n" + "[embed]http://youtu.be/Vpg9yizPP_g[/embed]\n" + "[embed] http://youtu.be/Vpg9yizPP_g [/embed]\n" + "<a href src=\"http://youtu.be/Vpg9yizPP_g\">vid</a>\n" + "<a href src=\"http://youtube.com/watch?feature=player_embedded&v=Vpg9yizPP_g\">vid</a>\n" + "<a href src=\"https://youtube.com/watch?v=Vpg9yizPP_g\">vid</a>"; final String subst = "\\1\\2\\3\\4"; final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL); final Matcher matcher = pattern.matcher(string); // The substituted value will be contained in the result variable final String result = matcher.replaceAll(subst); System.out.println("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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html