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

/
/
gimx

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 = "(?(DEFINE)\n" + " (?<quote>['\"])\n" + " (?<pair>\n" + " (?>\n" + " \\w+\n" + " |(?:\n" + " (?<pairQuote>(?&quote))[^'\"]+?\\k<pairQuote>\n" + " )\n" + " )\n" + " \\s*\\:\n" + " )\n" + " (?<string>\n" + " (?<stringQuote>(?&quote))[\\S\\s]*?(?<!\\\\)\\k<stringQuote>\n" + " )\n" + " (?<integer>\\-?\\d+(?:\\.\\d+)?(?:e[-+]\\d+)?)\n" + " (?<scalar>true|false|null|(?&integer))\n" + " (?<elements>\n" + " \\s*(?&value)\n" + " (?(R&array)|(?>(?:\\s*\\,(?&elements))|\\s*))\n" + " )\n" + " (?<array>\\[(?>(?&elements)|\\s*)\\])\n" + " (?<value>\n" + " (?&object)\n" + " |(?&string)\n" + " |(?&scalar)\n" + " |(?&array)\n" + " )\n" + " (?<members>\n" + " \\s*(?&pair)\\s*(?&value)\n" + " (?(R&object)|(?>(?:\\s*\\,(?&members))|\\s*))\n" + " )\n" + " (?<object>\\{(?&members)?\\})\n" + ")\n\n" + "\\A(?&object)\\Z"; final String string = "{\"menu\": {\n" + " \"header\": \"SVG Viewer\",\n" + " \"items\": [\n" + " {\"id\": \"Open\"},\n" + " {\"id\": \"OpenNew\", \"label\": \"Open New\"},\n" + " null,\n" + " {\"id\": \"ZoomIn\", \"label\": \"Zoom In\"},\n" + " {\"id\": \"ZoomOut\", \"label\": \"Zoom Out\"},\n" + " {\"id\": \"OriginalView\", \"label\": \"Original View\"},\n" + " null,\n" + " {\"id\": \"Quality\"},\n" + " {\"id\": \"Pause\"},\n" + " {\"id\": \"Mute\"},\n" + " null,\n" + " {\"id\": \"Find\", \"label\": \"Find...\"},\n" + " {\"id\": \"FindAgain\", \"label\": \"Find Again\"},\n" + " {\"id\": \"Copy\"},\n" + " {\"id\": \"CopyAgain\", \"label\": \"Copy Again\"},\n" + " {\"id\": \"CopySVG\", \"label\": \"Copy SVG\"},\n" + " {\"id\": \"ViewSVG\", \"label\": \"View SVG\"},\n" + " {\"id\": \"ViewSource\", \"label\": \"View Source\"},\n" + " {\"id\": \"SaveAs\", \"label\": \"Save As\"},\n" + " null,\n" + " {\"id\": \"Help\"},\n" + " {\"id\": \"About\", \"label\": \"About Adobe CVG Viewer...\"}\n" + " ],\n" + " \"test\": [\n" + " \"Some value\",\n" + " 4,\n" + " null,{}\n" + " ],\n" + " \"empty_array\":[-0.34E+4]\n" + "}}"; final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.COMMENTS); 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