Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests (1)

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "\\b((v.+)|(a|alpha.+)|(b|beta.+))?\\s?(\\d+\\.)?(\\d+\\.)?(\\*|\\d+).+((a|alpha.+)|(b|beta.+))?"; final String string = "Version 1.2.3\n" + "Ver 6.5.3\n" + "V 9.1\n" + "V 2016-2-20\n" + "Version 19-03.1970\n\n" + "Ver6.5.3\n" + "V9.1\n" + "V2016-2-20\n" + "Version19-03.1970\n\n" + "version 1.2.3\n" + "ver 6.5.3\n" + "v 9.1\n" + "v 2016-2-20\n" + "version 19-03.1970\n\n" + "ver6.5.3\n" + "v9.1\n" + "v2016-2-20\n" + "version19-03.1970\n\n" + "6.5.3\n" + "9.1\n" + "2016-2-20\n" + "19-03.1970\n\n" + "/****************************\n" + "* Sample Header Comment\n" + "* Created by Jane Programmer\n" + "* 2016-05-01\n" + "*\n" + "* Version 00.09 Beta\n" + "*/\n\n\n" + "##############################\n" + "# Sample Comment Test 2\n" + "# Created by Joe Cool (Snoppy)\n" + "# 12/31/1979\n" + "# \n" + "# V8 (beta)\n" + "####\n\n\n" + "V8.45.32 beta\n" + "v78.14.01 Alpha\n" + "Alpha 781.54.1\n\n" + "Beta 12.07.79\n\n" + "a1.2.3\n" + "b4.5.6-99\n"; final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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