Regular Expressions 101

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  • 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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

/
/
gm

Test String

Code Generator

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)^(?<fullAddress>(?<mailbox>([a-zA-Z0-9\+\!\#\$\%\&\'\*\-\/\=\?\+\_\{\}\|\~]|(?<singleDot>(?<!\.)(?<!^)\.(?!\.))|(?<foldedWhiteSpace>\s?\&\#13\;\&\#10\;.)){1,64})\s?(?<singleAt>(?<!\@)(?<!\-)(?<!\.)\@(?!\@))(?<domain>(?<dns>[[:alnum:]]([[:alnum:]\-]{0,63}\.){1,24}[[:alnum:]\-]{1,63}[[:alnum:]])|(?<IPv4>\[((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\])|(?<IPv6Full>(\[IPv6(\:[0-9a-fA-F]{1,4}){8}\]))|(?<IPv6Comp1>\[IPv6\:((([0-9a-fA-F]{1,4})\:){1,3}(\:([0-9a-fA-F]{1,4})){1,5}?\])|\[IPv6\:((([0-9a-fA-F]{1,4})\:){1,5}(\:([0-9a-fA-F]{1,4})){1,3}?\]))|(?<IPv6Comp2>(\[IPv6\:\:(\:[0-9a-fA-F]{1,4}){1,6}\]))|(?<IPv6Comp3>(\[IPv6\:([0-9a-fA-F]{1,4}\:){1,6}\:\]))|(?<IPv6Comp4>(\[IPv6\:\:\:)\])|(?<IPv6v4Full>(\[IPv6(\:[0-9a-fA-F]{1,4}){6}\:((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3})(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\])|(?<IPv6v4Comp1>\[IPv6\:((([0-9a-fA-F]{1,4})\:){1,3}(\:([0-9a-fA-F]{1,4})){1,5}?(\:((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))\])|\[IPv6\:((([0-9a-fA-F]{1,4})\:){1,5}(\:([0-9a-fA-F]{1,4})){1,3}?(\:((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))\]))|(?<IPv6v4Comp2>(\[IPv6\:\:(\:[0-9a-fA-F]{1,4}){1,5}(\:((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))\]))|(?<IPv6v4Comp3>(\[IPv6\:([0-9a-fA-F]{1,4}\:){1,5}\:(((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))\]))|(?<IPv6v4Comp4>(\[IPv6\:\:\:((?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3})(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\])))`) var str = `Valid (as per futility) addresses that I agree are valid ======================================================== _somename@iana.org test62 Valid _Yosemite.Sam@iana.org test128 Valid !def!xyz%abc@iana.org test61 Valid {_test_}@iana.org test90 Valid +1~1+@iana.org test89 Valid ~@iana.org test129 Valid $A12345@iana.org test60 Valid 1234567890@iana.org test85 Valid 1234567890123456789012345678901234567890123456789012345678@12345678901234567890123456789012345678901234567890123456789.12345678901234567890123456789012345678901234567890123456789.123456789012345678901234567890123456789012345678901234567890123.iana.org test9 Valid 1234567890123456789012345678901234567890123456789012345678901234@iana.org test2 Valid a-b@bar.com test202 Valid a@b.co-foo.uk test209 Valid a@bar.com test193 Valid aaa@[123.123.123.123] test197 Valid cdburgess+!#$%&'*-/=?+_{}|~test@gmail.com test229 Valid customer/department@iana.org test127 Valid customer/department=shipping@iana.org test59 Valid dclo@us.ibm.com test63 Valid first.last @iana.org test223 Valid first.last@[12.34.56.78] test10 Valid first.last@[IPv6:::] test233 Valid first.last@[IPv6:::1111:2222:3333:4444:5555:6666] test14 Valid first.last@[IPv6:::12.34.56.78] test11 Valid first.last@[IPv6:::a2:a3:a4:b1:ffff:11.22.33.44] test252 Valid first.last@[IPv6:::a3:a4:b1:ffff:11.22.33.44] test251 Valid first.last@[IPv6:1111:2222:3333::4444:5555:6666:7777] test45 Valid first.last@[IPv6:::b3:b4] test239 Valid first.last@[IPv6:::b4] test236 Valid first.last@[IPv6:0123:4567:89ab:cdef::] test249 Valid first.last@[IPv6:0123:4567:89ab:CDEF::] test250 Valid first.last@[IPv6:0123:4567:89ab:cdef::11.22.33.44] test262 Valid first.last@[IPv6:0123:4567:89ab:CDEF::11.22.33.44] test264 Valid first.last@[IPv6:1111:2222:3333::4444:12.34.56.78] test12 Valid first.last@[IPv6:1111:2222:3333::4444:5555:12.34.56.78] test38 Valid first.last@[IPv6:1111:2222:3333::4444:5555:6666] test15 Valid first.last@[IPv6:1111:2222:3333:4444:5555:6666::] test16 Valid first.last@[IPv6:1111:2222:3333:4444:5555:6666:12.34.56.78] test13 Valid first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:8888] test17 Valid first.last@[IPv6:a1::] test244 Valid first.last@[IPv6:a1::11.22.33.44] test258 Valid first.last@[IPv6:a1::b2:11.22.33.44] test270 Valid first.last@[IPv6:a1::b4] test241 Valid first.last@[IPv6:a1:a2::] test247 Valid first.last@[IPv6:a1:a2::11.22.33.44] test260 Valid first.last@[IPv6:a1:a2:a3:a4::11.22.33.44] test253 Valid first.last@[IPv6:a1:a2:a3:a4:b1::11.22.33.44] test254 Valid first.last@123.iana.org test20 Valid first.last@3com.com test19 Valid first.last@example.123 test48 Valid first.last@iana.org test1 Valid first.last@x23456789012345678901234567890123456789012345678901234567890123.iana.org test18 Valid foobar@192.168.0.1 test216 Valid Ima.Fool@iana.org test135 Valid name.lastname@domain.com test188 Valid peter.piper@iana.org test66 Valid shaitan@my-domain.thisisminekthx test214 Valid t*est@iana.org test88 Valid test-test@iana.org test87 Valid test. &#13;&#10; &#13;&#10; obs@syntax.com test224 Valid Test.&#13;&#10; Folding.&#13;&#10; Whitespace@iana.org test152 Valid test.test@iana.org test92 Valid test@[123.123.123.123] test98 Valid test@123.123.123.123 test97 Valid test@123.123.123.x123 test96 Valid test@example.example.iana.org test100 Valid test@example.iana.org test99 Valid test@iana.org test83 Valid TEST@iana.org test84 Valid test@test.com test277 Valid test@xn--example.com test279 Valid test+test@iana.org test86 Valid user%uucp!path@berkeley.edu test220 Valid user+mailbox@iana.org test58 Valid valid@about.museum test212 Valid Valid (as per futility) addresses that are invalid as per RFC5321 ============================================================================ +@b.c test203 Valid first.last@com test49 Valid a@b test190 Valid a@bar test201 Valid test@Bücher.ch test280 Valid test@example test116 Valid first.last@[IPv6:::a2:a3:a4:b1:b2:b3:b4] test230 Valid first.last@[IPv6:a1:a2:a3:a4:b1:b2:b3::] test231 Valid +@b.com test204 Valid My tests for valid IPv6 and v6v4 addresses ========================================== first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:8888] first.last@[IPv6:1111:2222:3333:4444:5555:6666:12.34.56.78] first.last@[IPv6:1111:2222:3333:4444:5555:6666::] first.last@[IPv6:1111:2222:3333:4444:5555::8888] first.last@[IPv6:1111:2222:3333:4444::7777:8888] first.last@[IPv6:1111:2222:3333::6666:7777:8888] first.last@[IPv6:1111:2222::5555:6666:7777:8888] first.last@[IPv6:1111::4444:5555:6666:7777:8888] first.last@[IPv6:::3333:4444:5555:6666:7777:8888] first.last@[IPv6:1111:2222:3333:4444:5555::] first.last@[IPv6:1111:2222:3333:4444::8888] first.last@[IPv6:1111:2222:3333::7777:8888] first.last@[IPv6:1111:2222::6666:7777:8888] first.last@[IPv6:1111::5555:6666:7777:8888] first.last@[IPv6:::4444:5555:6666:7777:8888] first.last@[IPv6:::3333:4444:5555:6666:7777:8888] first.last@[IPv6:1111:2222:3333:4444::12.34.56.78] first.last@[IPv6:1111:2222:3333::6666:12.34.56.78] first.last@[IPv6:1111:2222::5555:6666:12.34.56.78] first.last@[IPv6:1111::4444:5555:6666:12.34.56.78] first.last@[IPv6:::3333:4444:5555:6666:12.34.56.78] Invalid (as per futility) addresses with valid mailbox defective domain ======================================================================= x@x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x2 test8 Valid 123456789012345678901234567890123456789012345678901234567890@12345678901234567890123456789012345678901234567890123456789.12345678901234567890123456789012345678901234567890123456789.12345678901234567890123456789012345678901234567890123456789.12345.iana.org test21 Invalid first.last@[IPv6:1111:2222:33333::7777:8888] test47 Invalid aaa@[123.123.123.123]a test198 Invalid a@b-.com test206 Invalid a@bar.com. test200 Invalid a@-b.com test205 Invalid aaa@.123 test196 Invalid aaa@.com test195 Invalid aaa@[123.123.123.333] test199 Invalid abc@def@iana.org test69 Invalid doug@ test73 Invalid first.last@ test33 Invalid first.last@-xample.com test50 Invalid first.last@[::12.34.56.78] test37 Invalid first.last@[.12.34.56.78] test35 Invalid first.last@[12.34.56.789] test36 Invalid first.last@[IPv5:::12.34.56.78] test37 Invalid first.last@[IPv6::::] test234 Invalid first.last@[IPv6::::11.22.33.44] test256 Invalid first.last@[IPv6::::b3:b4] test240 Invalid first.last@[IPv6::::b4] test237 Invalid first.last@[IPv6::] test232 Invalid first.last@[IPv6::11.22.33.44] test255 Invalid first.last@[IPv6::a2::b4] test273 Invalid first.last@[IPv6::a2:a3:a4:b1:b2:b3:b4] test275 Invalid first.last@[IPv6::b3:b4] test238 Invalid first.last@[IPv6::b4] test235 Invalid first.last@[IPv6:0123:4567:89ab:cdef::11.22.33.xx] test263 Invalid first.last@[IPv6:0123:4567:89ab:CDEFF::11.22.33.44] test265 Invalid first.last@[IPv6:1111:2222::3333::4444:5555:6666] test44 Invalid first.last@[IPv6:1111:2222:3333:4444:5555:12.34.56.78] test40 Invalid first.last@[IPv6:1111:2222:3333:4444:5555:6666:12.34.567.89] test158 Invalid first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:12.34.56.78] test41 Invalid first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:8888:9999] test43 Invalid first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777] test42 Invalid first.last@[IPv6:1111:2222:333x::4444:5555] test46 Invalid first.last@[IPv6:a1:::] test245 Invalid first.last@[IPv6:a1:::11.22.33.44] test259 Invalid first.last@[IPv6:a1:::b4] test242 Invalid first.last@[IPv6:a1::11.22.33.44.55] test268 Invalid first.last@[IPv6:a1::11.22.33] test267 Invalid first.last@[IPv6:a1::a4:b1::b4:11.22.33.44] test266 Invalid first.last@[IPv6:a1::b2::11.22.33.44] test271 Invalid first.last@[IPv6:a1::b211.22.33.44] test269 Invalid first.last@[IPv6:a1::b3:] test272 Invalid first.last@[IPv6:a1:] test243 Invalid first.last@[IPv6:a1:11.22.33.44] test257 Invalid first.last@[IPv6:a1:a2:::] test248 Invalid first.last@[IPv6:a1:a2:::11.22.33.44] test261 Invalid first.last@[IPv6:a1:a2:] test246 Invalid first.last@[IPv6:a1:a2:a3:a4::b1:b2:b3:b4] test276 Invalid first.last@[IPv6:a1:a2:a3:a4:b1:b2:b3:] test274 Invalid first.last@exampl-.com test51 Invalid first.last@sub.do,com test3 Invalid first.last@x234567890123456789012345678901234567890123456789012345678901234.iana.org test52 Invalid foo@[\1.2.3.4] test149 Invalid gatsby@f.sc.ot.t.f.i.tzg.era.l.d. test82 Invalid Invalid@about.museum- test213 Invalid test@[123.123.123.123 test117 Invalid test@@iana.org test106 Invalid test@123.123.123.123] test118 Invalid test@123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012.com test115 Invalid test@example. test113 Invalid test@example.com&#10; test278 Invalid x@x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456 test34 Invalid Invalid (as per futility) addresses with valid domain defective mailbox ======================================================================= -- test --@iana.org test107 Invalid .@iana.org test133 Invalid .dot@iana.org test76 Invalid .first.last@iana.org test24 Invalid .test@iana.org test104 Invalid .wooly@iana.org test130 Invalid ()[]\;:,><@iana.org test111 Invalid [test]@iana.org test108 Invalid {^c\@**Dog^}@cartoon.com test161 Invalid @iana.org test72 Invalid 12345678901234567890123456789012345678901234567890123456789012345@iana.org test23 Invalid Abc\@def@iana.org test155 Invalid abc\@def@iana.org test64 Invalid abc\@iana.org test71 Invalid abc\\@def@iana.org test70 Invalid abc\\@iana.org test65 Invalid dot.@iana.org test77 Invalid first..last@iana.org test26 Invalid first.last.@iana.org test25 Invalid first(12345678901234567890123456789012345678901234567890)last@(1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890)iana.org test173 Invalid first(abc(\"def\".ghi).mno)middle(abc(\"def\".ghi).mno).last@(abc(\"def\".ghi).mno)example(abc(\"def\".ghi).mno).(abc(\"def\".ghi).mno)com(abc(\"def\".ghi).mno) test183 Invalid first(middle)last@iana.org test179 Invalid first\@last@iana.org test5 Invalid first\\@last@iana.org test32 Invalid first\last@iana.org test154 Invalid Fred\ Bloggs@iana.org test156 Invalid hello world@iana.org test81 Invalid Ima Fool@iana.org test138 Invalid Invalid \&#10; Folding \&#10; Whitespace@iana.org test218 Invalid Joe.\\Blow@iana.org test157 Invalid NotAnEmail test119 Invalid ote\"@iana.org test75 Invalid phil.h\@\@ck@haacked.com test139 Invalid pootietang.@iana.org test132 Invalid test..test@iana.org test103 Invalid test.@iana.org test102 Invalid test.&#13;&#10;&#13;&#10; obs@syntax.com test225 Invalid test.iana.org test101 Invalid test@. test112 Invalid test@...........com test215 Invalid test@.org test114 Invalid test@test@iana.org test105 Invalid two..dot@iana.org test78 Invalid Unicode NULL \\\u0000@char.com test228 Invalid wo..oly@iana.org test131 Invalid Invalid (as per futility) addresses with defective mailbox and domain ======================================================================= -- test --@iana.org test107 Invalid -@..com test207 Invalid -@a..com test208 Invalid .@ test189 Invalid @@bar.com test192 Invalid @bar.com test191 Invalid @NotAnEmail test120 Invalid aaa.com test194 Invalid first.last test22 Invalid Valid (as per futility) addresses that use parenthesis or quotes ================================================================ &#13;&#10; (&#13;&#10; x &#13;&#10; ) &#13;&#10; first&#13;&#10; ( &#13;&#10; x&#13;&#10; ) &#13;&#10; .&#13;&#10; ( &#13;&#10; x) &#13;&#10; last &#13;&#10; ( x &#13;&#10; ) &#13;&#10; @iana.org test222 Valid 1234 @ local(blah) .machine .example test178 Valid a(a(b(c)d(e(f))g)h(i)j)@iana.org test186 Valid c@(Chris's host.)public.example test176 Valid cal(foo\)bar)@iamcal.com test167 Valid cal(foo\@bar)@iamcal.com test166 Valid cal(woo(yay)hoopla)@iamcal.com test165 Valid cal@iamcal(woo).(yay)com test163 Valid first.last@x(1234567890123456789012345678901234567890123456789012345678901234567890).com test185 Valid HM2Kinsists@(that comments are allowed)this.is.ok test219 Valid jdoe@machine(comment). example test177 Valid first.(\")middle.last(\")@iana.org test182 Valid first.(&#13;&#10; middle&#13;&#10; )last@iana.org test172 Valid first.\"last\"@iana.org test144 Valid first.\"mid\\dle\".\"last\"@iana.org test151 Valid first(Welcome to&#13;&#10; the (\"wonderful\" (!)) world&#13;&#10; of email)@iana.org test174 Valid pete(his account)@silly.test(his host) test175 Valid first().last@iana.org test171 Valid first(a\"bc.def).last@iana.org test181 Valid first(abc.def).last@iana.org test180 Valid first(abc\(def)@iana.org test184 Valid first().last@iana.org test171 Valid first(a\"bc.def).last@iana.org test181 Valid first(abc.def).last@iana.org test180 Valid first(abc\(def)@iana.org test184 Valid (foo)cal(bar)@(baz)iamcal.com(quux) test162 Valid test.\"test\"@iana.org test94 Valid "\"Unicode NULL \\\u0000\"@char.com test226 Valid \"[[ test ]]\"@iana.org test91 Valid \"Abc@def\"@iana.org test56 Valid \"Abc\\@def\"@iana.org test53 Valid \"Austin@Powers\"@iana.org test134 Valid \"Doug \\\"Ace\\\" L.\"@iana.org test68 Valid \"first..last\"@iana.org test148 Valid \"first.middle.last\"@iana.org test147 Valid \"first.middle\".\"last\"@iana.org test146 Valid \"first(last)\"@iana.org test221 Valid \"first@last\"@iana.org test6 Valid \"first\".\"last\"@iana.org test140 Valid \"first\".\"middle\".\"last\"@iana.org test145 Valid \"first\".last@iana.org test143 Valid \"first\".middle.\"last\"@iana.org test141 Valid \"first\\\"last\"@iana.org test4 Valid \"first\\\\\\\"last\"@iana.org test150 Valid \"first\\\\last\"@iana.org test7 Valid \"first\\last\"@iana.org test28 Valid \"Fred Bloggs\"@iana.org test57 Valid \"Fred\\ Bloggs\"@iana.org test54 Valid \"hello my name is\"@stutter.com test210 Valid \"Ima Fool\"@iana.org test137 Valid \"Ima.Fool\"@iana.org test136 Valid \"Joe.\\\\Blow\"@iana.org test55 Valid \"Joe\\\\Blow\"@iana.org test217 Valid \"Test \\\"Fail\\\" Ing\"@iana.org test211 Valid \"test.test\"@iana.org test93 Valid \"test@test\"@iana.org test95 Valid \"test\\\"blah\"@iana.org test125 Valid \"test\\\\blah\"@iana.org test121 Valid \"test\\&#13;blah\"@iana.org test123 Valid \"test\\blah\"@iana.org test122 Valid \"test\\test\"@iana.org test109 Valid \"test&#13;&#10; blah\"@iana.org test160 Valid Invalid (as per futility) addresses that use parenthesis or quotes ================================================================== \"\"@iana.org test31 Invalid \"\"\"@iana.org test29 Invalid \"\\\"@iana.org test30 Invalid \"Doug \"Ace\" L.\"@iana.org test79 Invalid \"first\"last\"@iana.org test27 Invalid \"first\\\\\"last\"@iana.org test142 Invalid \"foo\"(yay)@(hoopla)[1.2.3.4] test164 Invalid \"qu@iana.org test74 Invalid \"test\"blah\"@iana.org test126 Invalid \"test\"test\"@iana.org test110 Invalid \"test\&#13;&#10; blah\"@iana.org test159 Invalid \"test&#13;blah\"@iana.org test124 Invalid \"Unicode NULL \u0000\"@char.com test227 Invalid a(a(b(c)d(e(f))g)(h(i)j)@iana.org test187 Invalid cal(foo(bar)@iamcal.com test168 Invalid cal(foo)bar)@iamcal.com test196 Invalid cal(foo\)@iamcal.com test170 Invalid Doug\\ \\\"Ace\\\"\\ L\\.@iana.org test80 Invalid Doug\\ \\\"Ace\\\"\\ Lovell@iana.org test67 Invalid first.\"\".last@iana.org test153 Invalid` 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/