Regular Expressions 101

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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

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)^(?P<email>(?P<local>(?![\.\ ]+)(?=[^@]+)(?:(?:(?:[\#\!\$\%\&\'\*\+\-\/\=\?\^\_\`\{\|\}\~\p{L}\p{N}])*(?:(?<=\.|^)(?:\"(?:[^\"]|(?<=\\)[\"\(\)\,\:\;\<\>\@\[\\\]])*\")\.?)*(?:[\#\!\$\%\&\'\*\+\-\/\=\?\^\_\`\{\|\}\~\p{L}\p{N}])*)))(?<!\.)\@(?P<host>(?:[\w\-]+?\.?)*|\[[\w\d\:]*\])(?![\.\ ]+))$`) var str = `EMAIL ________ john.smith(comment)@example.com (comment)john.smith@example.com john.smith@(comment)example.com john.smith@example.com(comment) abc."defghi".xyz@example.com "abcdefghixyz"@example.com "John..Doe"@example.com "test"."test"@test.com test."test"@test.com "test".test@test.com "\""@test.com "\"\"".test@test.com prettyandsimple@example.com very.common@example.com disposable.style.email.with+symbol@example.com other.email-with-dash@example.com x@example.com "much.more unusual"@example.com "very.unusual.@.unusual.com"@example.com "very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com example-indeed@strange-example.com admin@mailserver1 #!$%&'*+-/=?^_\`{}|~@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` 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/