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

/
/

Test String

Code Generator

Language

Generated Code

const regex = /^(?<hostip>[^ ]+) - - \[(?<timestamp>[^ ]+)\s-(?<unknown1>\d+)] "(?<method>[^ ]+) (?<request>[^ ]+) HTTP\/\d\.\d" (?<response>\d+) - (?<bytes>\d+)/; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?<hostip>[^ ]+) - - \\[(?<timestamp>[^ ]+)\\s-(?<unknown1>\\d+)] "(?<method>[^ ]+) (?<request>[^ ]+) HTTP\\\/\\d\\.\\d" (?<response>\\d+) - (?<bytes>\\d+)', '') const str = `10.170.63.247 - - [16/Jun/2015:10:25:56 -0400] "GET /iconic/staticContentBuild/js/jquery-1.8.2.js HTTP/1.1" 200 - 580 SMUSER=- remote-client-ip=10.29.110.51 http_referer=- Agent=Mozilla/5.0 (iPad; CPU OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 10.170.63.247 - - [16/Jun/2015:10:25:56 -0400] "GET /retail/staticContentBuild/js/pos-module.js HTTP/1.1" 200 - 120 SMUSER=- remote-client-ip=10.164.96.28 http_referer=- Agent=Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET CLR 1.1.4322; .NET4.0C; .NET4.0E) 10.170.63.247 - - [16/Jun/2015:10:25:56 -0400] "GET /retail/mobilepos/screens/ETR2/styles/omnilink.css HTTP/1.1" 200 - 170 SMUSER=- remote-client-ip=10.27.174.140 http_referer=- Agent=Mozilla/5.0 (iPad; CPU OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 10.170.63.247 - - [16/Jun/2015:10:25:57 -0400] "GET /retail/staticContentBuild/images/queue_icon_greyw.png HTTP/1.1" 200 - 230 SMUSER=- remote-client-ip=10.167.154.165 http_referer=- Agent=Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; Tablet PC 2.0; .NET CLR 1.1.4322) 10.170.63.247 - - [16/Jun/2015:10:25:57 -0400] "GET /retail/staticContentBuild/js/handlebar-data.js HTTP/1.1" 200 - 140 SMUSER=- remote-client-ip=10.166.12.56 http_referer=- Agent=Mozilla/5.0 (iPad; CPU OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 10.144.62.247 - - [16/Jun/2015:10:25:57 -0400] "GET /retail/mobilepos/screens/ETR2/scripts/templates/device-details/modals/reset-voicemail-password/resetVoicemailPasswordItemView.tmpl HTTP/1.1" 200 - 180 SMUSER=- remote-client-ip=10.130.4.66 http_referer=- Agent=Mozilla/5.0 (iPad; CPU OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 10.170.63.247 - - [16/Jun/2015:10:25:57 -0400] "GET /iconic/staticContentBuild/js/accountLines.js HTTP/1.1" 200 - 240 SMUSER=- remote-client-ip=10.164.18.46 http_referer=- Agent=Mozilla/5.0 (iPad; CPU OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; if ((m = regex.exec(str)) !== null) { // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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 JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions