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

// include the latest version of the regex crate in your Cargo.toml extern crate regex; use regex::Regex; fn main() { let regex = Regex::new(r#"(?m)^(?P<email>(?P<local>(?![\.\ ]+)(?=[^@]+)(?:(?:(?:[\#\!\$\%\&\'\*\+\-\/\=\?\^\_\`\{\|\}\~\p{L}\p{N}])*(?:(?<=\.|^)(?:\"(?:[^\"]|(?<=\\)[\"\(\)\,\:\;\<\>\@\[\\\]])*\")\.?)*(?:[\#\!\$\%\&\'\*\+\-\/\=\?\^\_\`\{\|\}\~\p{L}\p{N}])*)))(?<!\.)\@(?P<host>(?:[\w\-]+?\.?)*|\[[\w\d\:]*\])(?![\.\ ]+))$"#).unwrap(); let string = "EMAIL ________ john.smith(comment)@example.com (comment)john.smith@example.com john.smith@(comment)example.com john.smith@example.com(comment) abc.\"defghi\".xyz@example.com \"abcdefghixyz\"@example.com \"John..Doe\"@example.com \"test\".\"test\"@test.com test.\"test\"@test.com \"test\".test@test.com \"\\\"\"@test.com \"\\\"\\\"\".test@test.com prettyandsimple@example.com very.common@example.com disposable.style.email.with+symbol@example.com other.email-with-dash@example.com x@example.com \"much.more unusual\"@example.com \"very.unusual.@.unusual.com\"@example.com \"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com example-indeed@strange-example.com admin@mailserver1 #!$%&'*+-/=?^_`{}|~@example.org \"()<>[]:,;@\\\\\\\"!#$%&'-/=?^_`{}| ~.a\"@example.org \" \"@example.org example@localhost example@s.solutions user@localserver user@tt user@[IPv6:2001:DB8::1] ________ @test.com abc\\\"def\\\"ghi@example.com abc\"defghi\"xyz@example.com John..Doe@example.com Abc.example.com A@b@c@example.com \"\\\"\"\".\"\"@test.com test\"@test.com .\"\".@test.com a\"b(c)d,e:f;g<h>i[j\\k]l@example.com just\"not\"right@example.com this is\"not\\allowed@example.com this\\ still\\\"not\\\\allowed@example.com john..doe@example.com john.doe@example..com.somethingelse.something.more..more john.doe@example.com john.doe@example.com .john.doe@something.com johndoe.@something.com"; // result will be an iterator over tuples containing the start and end indices for each match in the string let result = regex.captures_iter(string); for mat in result { println!("{:?}", mat); } }

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 Rust, please visit: https://docs.rs/regex/latest/regex/