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

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

/
/
mg

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 = "^((?! xxxx-xx-xx)((19|20|x)[0-9x][0-9x])\\-((02\\-(-[1-9]|[1-2]\\d|xx))|((04|06|09|11)\\-(0[1-9]|[1-2]\\d|30|xx))|((01|03|05|07|08|10|12|xx)\\-(0[1-9]|[1-2]\\d|30|31|xx)))((?! xx:xx:xx) ([0-1]\\d|2[0-3]|xx):([0-5]\\d|xx)(:([0-5]\\d|xx)|))?)$"; final String string = "xxxx-xx-xx\n" + "2011-12-22\n" + "2014-10-11\n" + "2014-10-17 08:11:11\n" + "2014-10-10 xx:10:xx\n" + "2014-10-21 xx:xx\n" + "2014-10-01 10:xx:xx\n" + "2014-10-03 xx:10:xx\n" + "2014-10-14 xx:xx:10\n" + "2014-10-13 10:10:xx\n" + "2014-10-15 xx:10:10\n" + "2014-10-16 10:xx:10\n" + "2014-10-17 10:11:10\n" + "xxxx-xx-xx 10:11:10\n" + "2014-10-18 xx:xx:xx\n" + "xxxx-xx-xx xx:xx:01\n" + "xxx-xx-xx xx:xx:01\n" + "xxx-xx-xx xx:xx:xx\n" + "xxxx-xx-xx xx:xx:xx"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); 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