Regular Expressions 101

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  • PCRE2 (PHP >=7.3)
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  • ECMAScript (JavaScript)
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  • Java 8
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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
  • A character except: a, b or c
  • A character in the range: a-z
  • A character not in the range: a-z
  • A character in the range: a-z or A-Z
  • Any single character
  • Alternate - match either a or b
  • Any whitespace character
  • Any non-whitespace character
  • Any digit
  • Any non-digit
  • Any word character
  • Any non-word character
  • Match everything enclosed
  • Capture everything enclosed
  • Zero or one of a
  • Zero or more of a
  • One or more of a
  • Exactly 3 of a
  • 3 or more of a
  • Between 3 and 6 of a
  • Start of string
  • End of string
  • A word boundary
  • Non-word boundary

Regular Expression
No Match


Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"^[a-z][a-z]*(([A-Z]{1,3}[a-z]+)*[A-Z]{0,3}|([a-z]+[A-Z]{1,3})*|[A-Z]{1,3})$"; string input = @"snake_case PascalCase 2PascalCase streamIOIO gREATERDtha modeADFAFdsADFads aBabcABCDabcABC lThan30DaysCount lessThan30DaysCount lessThan30DaysCountA greaterThan30LessThan60DaysCount greaterThan60LessThan90DaysCount greaterThan90DaysCount aabc123 gREA1 cP3 a1 a123 a1G hELLO camel01C camel01c01 camel01C01 camel01CC01 camel0a1c1 camel0a1C1 camel0ac1b1C1 mode2A mode2A2 mode2A2A pascal2Case pascal2CaseA contextHTMLParser camelCa1 camelCa_1 supportsIpv6OnIos affine3D camelC1 modeADFdsADFads streamIO aBCabcABCabcA aBCabcA aabcABC ab abc abcd abcde deviceSNS pathASNs dscpCP awsVPC serialNo deviceID camelCasecamelCasecamelCasecamelCasecamelCasecamelCase gREAt gREAtREAt aABC modeADFsADFads aG a modeADFads camelCase pascalCase pascalCaseA modeA createAMode createBMode madeEasy wonderFul andMe htmlParser h aaA camelC camelCA ibsReleaseTestVerificationRegressionSuite ibsReleaseTestVerificationRegressioNSuite ibsReleaseTestVerificationRegressioN xmlHttpRequest newCustomerId innerStopwatch youTubeImporter youtubeImporter"; RegexOptions options = RegexOptions.Multiline; 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: