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

/
/
gi

Test String

Code Generator

Language

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(<.+?)(?<=\s)on[a-z]+\s*=\s*(?:(['""])(?!\2).+?\2|(?:\S+?\(.*?\)(?=[\s>])))(.*?>)"; string input = @"<meta name=""keywords"" content=""keyword1, keyword2, keyword3""> <a href=""something"" onclick= ""bad()"">text</a> onclick not in tags <a href=""something"" onclick =bad()>text</a> <a href=""something"" onclick=bad('test')>text</a> <a href=""something"" onclick=bad(""test"")>text</a> <a href=""something"" onclick=""bad()"" >text</a> <a href=""http://mydomain.com/index.php?oninaval=12"" class=""titi"">text</a> What if I write john+onelia=love forever? <a href=""something"" onclick=""bad()"">text</a> onclick not in tags <a href=""something"" onclick=bad()>text</a> <a href=""something"" onclick=""bad()"" >text</a> <a href=""something"" onclick=a++ >text</a> onclick=""asd <span class=""myclass""> not in tag too.</span> <!-- onclick="" --><a href=""something"" onclick= ""bad()"">text</a> <textarea><enter onclick=""dothat()"" text here></textarea> yoko ono=""john lennon"" <img src=""/images/img1.jpg"" alt=""onclick=thegood() onclick=thebad() ""/> <img alt=""onclick="" src=/images/theugly.jpg> the most important part of the message <p class=""disappears""></p> <a href="" onmouseover=a=7>button1</a> <a href=""something"" onclick=a++>text</a> <a href=""something"" onclick=a<<1>text</a> <a href="" onmouseover=""alert(a);"">button2</a>"; RegexOptions options = RegexOptions.IgnoreCase; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx