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

/
/
gm

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 = "(^#[0-9A-Fa-f]{6}$)|(^#[0-9A-Fa-f]{3,4}$)|(^#[0-9A-Fa-f]{8}$)"; final String string = "// good case\n" + "#000\n" + "#123\n" + "#999\n" + "#AAA\n" + "#aaa\n" + "#abc\n" + "#FFF\n" + "#0000\n" + "#9999\n" + "#AAAA\n" + "#aaaa\n" + "#abcd\n" + "#FFFF\n" + "#ffff\n" + "#000000\n" + "#456789\n" + "#999999\n" + "#AAAAAA\n" + "#aaaaaa\n" + "#abcdef\n" + "#FFFFFF\n" + "#ffffff\n" + "#00000000\n" + "#12345678\n" + "#99999999\n" + "#AAAAAAAA\n" + "#aaaaaaaa\n" + "#abcdefcc\n" + "#FFFFFFFF\n" + "#ffffffff\n" + "#00123456\n\n\n" + "//bad case\n" + "##\n" + "#0\n" + "#1\n" + "#F\n" + "#f\n" + "#12\n" + "#AB\n" + "#ae\n" + "#aaaaa\n" + "#fffff\n" + "#aaaah\n" + "#aaaaaaa\n" + "#0000000\n" + "#ffffhij\n" + "#h000000\n" + "#aaaaaaai\n" + "#000k0123\n" + "#asdfasfa\n\n"; 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