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

/
/
x

Test String

Code Generator

Language

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(?(DEFINE) # Note that everything is atomic, JSON does not need backtracking if it's valid # and this prevents catastrophic backtracking (?<json>(?>\s*(?&object)\s*|\s*(?&array)\s*)) (?<object>(?>\{\s*(?>(?&pair)(?>\s*,\s*(?&pair))*)?\s*\})) (?<pair>(?>(?&STRING)\s*:\s*(?&value))) (?<array>(?>\[\s*(?>(?&value)(?>\s*,\s*(?&value))*)?\s*\])) (?<value>(?>true|false|null|(?&STRING)|(?&NUMBER)|(?&object)|(?&array))) (?<STRING>(?>""(?>\\(?>[""\\\/bfnrt]|u[a-fA-F0-9]{4})|[^""\\\0-\x1F\x7F]+)*"")) (?<NUMBER>(?>-?(?>0|[1-9][0-9]*)(?>\.[0-9]+)?(?>[eE][+-]?[0-9]+)?)) ) \A(?&json)\z"; string input = @"[ ""JSON Test Pattern pass1"", {""object with 1 member"":[""array with 1 element""]}, {}, [], -42, true, false, null, { ""integer"": 1234567890, ""real"": -9876.543210, ""e"": 0.123456789e-12, ""E"": 1.234567890E+34, "": 23456789012E66, ""zero"": 0, ""one"": 1, ""space"": "" "", ""quote"": ""\"", ""backslash"": ""\\"", ""controls"": ""\b\f\n\r\t"", ""slash"": ""/ & \/"", ""alpha"": ""abcdefghijklmnopqrstuvwyz"", ""ALPHA"": ""ABCDEFGHIJKLMNOPQRSTUVWYZ"", ""digit"": ""0123456789"", ""0123456789"": ""digit"", ""special"": ""`1~!@#$%^&*()_+-={':[,]}|;.</>?"", ""hex"": ""\u0123\u4567\u89AB\uCDEF\uabcd\uef4A"", ""true"": true, ""false"": false, ""null"": null, ""array"":[ ], ""object"":{ }, ""address"": ""50 St. James Street"", ""url"": ""http://www.JSON.org/"", ""comment"": ""// /* <!-- --"", ""# -- --> */"": "" "", "" s p a c e d "" :[1,2 , 3 , 4 , 5 , 6 ,7 ],""compact"":[1,2,3,4,5,6,7], ""jsontext"": ""{\""object with 1 member\"":[\""array with 1 element\""]}"", ""quotes"": ""&#34; \u0022 %22 0x22 034 &#x22;"", ""\/\\\""\uCAFE\uBABE\uAB98\uFCDE\ubcda\uef4A\b\f\n\r\t`1~!@#$%^&*()_+-=[]{}|;:',./<>?"" : ""A key can be any string"" }, 0.5 ,98.6 , 99.44 , 1066, 1e1, 0.1e1, 1e-1, 1e00,2e+00,2e-00 ,""rosebud""]"; RegexOptions options = RegexOptions.IgnorePatternWhitespace; Match m = Regex.Match(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