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)(?:(?<display>[^<>\n]+)<)?(?<local>(?:[^\n \x22,\.:;<>@\[\\\]]{1,64}|[^\n \x22,.:;<>@\[\\\]]{1,32}\.[^\n \x22,.:;<>@\[\\\]]{1,32}|\x22[^\n]{1,62}\x22))@(?<domain>[\w.]+(?:\.\w{1,4})?|\[(?:IPv6)?[\da-fA-F.:]+\])>?`) var str = ` VALID Ihavea(comment)tosay@thisistrue.com John doe<john@doe.com> simple@example.com very.common@example.com FirstName.LastName@EasierReading.org x@example.com long.email-address-with-hyphens@and.subdomains.example.com user.name+tag+sorting@example.com user.name@example.com name/surname@example.com admin@example example@s.example " "@example.org "john..doe"@example.org mailhost!username@example.org "very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com user%example.com@example.org user-@example.org postmaster@[123.123.123.123] postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334] _test@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334] I❤️CHOCOLATE@example.com INVALID .hey@boss.com yo.hi.hello@man. abc.example.com john..doe@hi.com a@b@c@example.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 1234567890123456789012345678901234567890123456789012345678901234+x@example.com i.like.underscores@but_they_are_not_allowed_in_this_part` 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/