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

r"
"

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 = "(?P<remote_addr>(?:^|\\b(?<!\\.))(?:1?\\d\\d?|2[0-4]\\d|25[0-5])(?:\\.(?:1?\\d\\d?|2[0-4]\\d|25[0-5])){3}(?=$|[^\\w.]))\\s-\\s(?P<remote_usr>-|[a-z_][a-z0-9_]{0,30})\\s(?P<date_time>\\[(?P<date>[0-2][0-9]\\/\\w{3}\\/[12]\\d{3}):(?P<time>\\d\\d:\\d\\d:\\d\\d).*\\])\\s(?P<request>\\\"(?P<req_method>GET|POST|HEAD|PUT|DELETE|CONNECT|OPTIONS|TRACE|PATCH)\\s(?P<req_uri>\\/[^\\s]*)\\s(?P<http_ver>HTTP/\\d\\.\\d)\\\")\\s(?P<status>\\d{3})\\s(?P<body_byte_sent>\\d+)\\s\\\"(?P<http_referer>[^\\s]+)\\\"\\s\\\"(?P<user_agent>[^\\\"]+)\\\"\\s\\\"(?P<forward_for>[^\\\"]+)\\\""; final String string = "110.233.182.14 - - [03/Aug/2017:00:52:02 +0900] \"GET / HTTP/1.1\" 200 9017 \"-\" \"Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36\" \"110.233.182.14\""; final Pattern pattern = Pattern.compile(regex); final Matcher matcher = pattern.matcher(string); if (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