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 = "(?:-|(?P<real_ip>[\\-\\da-f.:, ]+)) - (?<remote_user>\\S+) \\[(?<timestamp>[^\\]]+)\\]\\s+\"(?:\\-|(?<request>\\w+) (?<request_uri>[^ \\?]+)(?:\\?(?<request_uri_query>[^ ]*))? (?<request_version>[\\w\\/\\.]+))\"\\s+(?P<status>[1-9]\\d{2})\\s+(?P<body_bytes_sent>\\d+)\\s+\"(?<http_referer>[^\"]+)\"\\s+\"(?<http_user_agent>[^\"]+)\"\\s+\"(?P<remote_ip>[\\da-f.:]+)\" (?:\\-|(?P<upstream_response_time>\\d+(?:.\\d+)?))\\s+(?P<request_time>\\d+(?:.\\d+)?) (?P<pipe>[\\.p])"; final String string = "10.100.7.118 - - [02/Aug/2022:19:27:57 +0800] \"GET /api/article/list/news HTTP/1.1\" 200 103594 \"https://165.npa.gov.tw/\" \"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36\" \"172.27.31.231\" 0.062 0.062 .\n\n" + "49.216.25.168, 203.66.34.45 - - [02/Aug/2022:19:28:10 +0800] \"GET /assets/i18n/zh-tw.json HTTP/1.1\" 200 9760 \"https://165.npa.gov.tw/\" \"Mozilla/5.0 (iPhone; CPU iPhone OS 15_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148\" \"172.27.31.231\" 0.031 0.031 .\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