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'''
'''
gmxi

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?mi)(?#First, match the protocol) (?:https?|ftp):// (?#Next, check for optional username and/or password) (?#Note: The following two char classes are functionally equivalent) (?:[\x21-\x39\x3b-\x3f\x41-\x7e]+(?::[!-9;-?A-~]+)?@)? (?#Next, let's match the domain [with support for Punycode ]) (?:xn--[0-9a-z]+|[0-9A-Za-z_-]+\.)*(?:xn--[0-9a-z]+|[0-9A-Za-z-]+)\.(?:xn--[0-9a-z]+|[0-9A-Za-z]{2,10}) (?#Let's match on optional port) (?::(?:6553[0-5]|655[0-2]\d|65[0-4]\d{2}|6[0-4]\d{3}|[1-5]\d{4}|[1-9]\d{1,3}|\d))? (?#Next, let's match on the path) (?:/[\x21\x22\x24\x25\x27-x2e\x30-\x3b\x3e\x40-\x5b\x5d-\x7e]*)* (?#Next, let's match on an anchor) (?:\#[\x21\x22\x24\x25\x27-x2e\x30-\x3b\x3e\x40-\x5b\x5d-\x7e]*)? (?#Last, but not least, we match on URI params) (?:\?[\x21\x22\x24\x25\x27-\x2e\x30-\x3b\x40-\x5b\x5d-\x7e]+=[\x21\x22\x24\x25\x27-\x2e\x30-\x3b\x40-\x5b\x5d-\x7e]*)? (?#Additional params) (?:&[\x21\x22\x24\x25\x27-\x2e\x30-\x3b\x40-\x5b\x5d-\x7e]+=[\x21\x22\x24\x25\x27-\x2e\x30-\x3b\x40-\x5b\x5d-\x7e]*)* `) var str = `https://thechildrenareourfuture.org/#SomeRandomAnchorGoesHere http://user:pass@example.com:8080/omega:33 https://www.google.com:65535/ https://www.google.com:42069/ https://www.google.com:9876/ https://www.google.com:59999/ https://www.google.com:10000/ https://www.google.com:1234/ https://www.google.com:53/ https://www.google.com:123/ https://www.google.com:0/ ftp://username:password@example.com:21/path/here/to/file.tar.gz http://google.com?redirect=https%3A%2F%2Flocalhost%3A8080&var2=somethingelse https://john.smith@github.com/UserGroup/repo.git https://mattermost.com:8065/team/messages/@john.smith https://punycode.xn--j6w193g smtp://somesite.com/myFile.php SMTP://SOMESITE.COM/MYFILE.PHP unknown://somesite.com/fiLeNuM12345.php //SomeSite.ru/foO.php ://SomeOtherSite.oRg/baRR.php https://_sub1.sub2.sub3.s-u_b4.domain.com http://username:password@subdomain.domain.co.uk/path/to/file.html#Anchor1?key1=value1&key2=value2` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", 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 Golang, please visit: https://golang.org/pkg/regexp/