Unexpected behaviour of regex validating email

Question

I am validating an email address using the following regex

var regex=/^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;

Now the problem is that it is showing unexpected behavior

If I enter email address like

[email protected]

This is accepted by the above regex as validate format of email address But when I use format

[email protected]

The regex don't validate it as email format

similarly

[email protected]

is a not a validate format while

[email protected]

is a validate email format I especially want the validity of email address of the format

[email protected]

What kind of mistake I am doing in above regex?

Can the problem be outside of the regex? Testing with this tool: spaweditor.com/scripts/regex/index.php there seems to be no problem.. — Arend
– Arend, Commented Jun 7, 2011 at 7:01
There are (public) top level domains with more than 4 letters in them, which that regex will reject. — Quentin
– Quentin, Commented Jun 7, 2011 at 7:02
Email addresses which include a + somewhere before the @ are quite common, and that regex will reject them. — Quentin
– Quentin, Commented Jun 7, 2011 at 7:03
@Quentin hi thanks for response. But in my format it is not having + sign? Iam only having . sign. Then why it not validating? — Awais Qarni
– Awais Qarni, Commented Jun 7, 2011 at 7:04
If I was answering the question, I would have given an answer. I'm just pointing out that the regex is horribly flawed in ways you aren't testing for. — Quentin
– Quentin, Commented Jun 7, 2011 at 9:03

orlp · Accepted Answer · 2011-06-07 07:15:43Z

An email address as defined by the RFC 822 (superseded by RFC 2822) is a very complex regex. In the original RFC it is defined as a recursive descent. This makes it very hard to express it in a regex. See this "article": http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html

In perl-style regex:

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ 
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\
r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[
 \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)
?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t]
)*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[
 \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)
*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+
|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r
\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t
]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031
]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](
?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?
:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?
:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?
[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|
\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>
@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"
(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[
\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-
\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(
?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;
:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([
^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"
.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\
]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\
[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\
r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] 
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]
|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \0
00-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\
.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,
;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?
:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[
^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]
]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(
?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[
\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t
])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t
])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?
:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|
\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:
[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\
]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)
?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["
()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)
?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>
@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[
 \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,
;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:
\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[
"()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])
*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])
+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\
.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)

Another article on e-mail addresses and regular expressions: regular-expressions.info/email.html
I hate that article. "my claim only holds true when one accepts my definition of what a valid email address really is". Yes, well, I live in the real world and would rather not kick my customers because they have a real, working email address that doesn't meet some guy's non-standard definition.

Bohemian · Accepted Answer · 2011-06-07 07:11:33Z

3

Firstly, don't escape characters in a character class ie [.] means a literal dot. Don't code as [\.]

Secondly, the dash character must be either the first or last character in a character class, otherwise it's the range operator.

Try this: Edited to include @BenRoux's \w suggestion

var regex=/^([\w.-])+\@([\w.-])+\.([A-Za-z]{2,4})$/

p.s. I tested it and this regex matches "[email protected]"

edited Jun 7, 2011 at 7:11

answered Jun 7, 2011 at 7:04

Bohemian♦

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4 Comments

Ben Roux Over a year ago

+1 for your comment regarding a hyphen inside of brackets... never knew about that. I always escaped it (though I hated to do so)

stema Over a year ago

its allowed to escape characters in a character class (but for most characters not needed), so [\.] will match a dot. If you want to match a backslash you have to escape it [\\], otherwise things like [\w] would match a backslash and a w and not a word character.

Awais Qarni Over a year ago

I have used your both formats. It is still not validating [email protected]. But is is validating [email protected]. Then what is the problem?

Bohemian Over a year ago

Sorry, I validated it using java and they both pass for me.

shinkou · Accepted Answer · 2011-06-07 07:17:29Z

3

If you really want to validate using javascript + regex, try this ridiculously long one. I've been using it for quite some time and no problem has come up so far.

var regex = /^(?:"(?:[^\\"]|\\.)+"|[A-Za-z0-9!#$%&'\*\+\-\/=\?^_`{|}~]+(?:\.[A-Za-z0-9!#$%&'\*\+\-\/=\?^_`{|}~]+)*)@(?:[A-Za-z](?:[A-Za-z0-9\-]{0,61}[A-Za-z0-9])?(?:\.[A-Za-z](?:[A-Za-z0-9\-]{0,61}[A-Za-z0-9])?)*|\[(?:(?:2(?:[0-4]\d|5[0-5])|[0-1]?\d{1,2})(?:\.(?:2(?:[0-4]\d|5[0-5])|[0-1]?\d{1,2})){3}|(?:(?:(?:[0-9A-Fa-f]{1,4}\:){1,1}(?:\:[0-9A-Fa-f]{1,4}){1,6})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,2}(?:\:[0-9A-Fa-f]{1,4}){1,5})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,3}(?:\:[0-9A-Fa-f]{1,4}){1,4})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,4}(?:\:[0-9A-Fa-f]{1,4}){1,3})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,5}(?:\:[0-9A-Fa-f]{1,4}){1,2})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,6}(?:\:[0-9A-Fa-f]{1,4}){1,1})|(?:[0-9A-Fa-f]{1,4}(?:\:[0-9A-Fa-f]{1,4}){7})|(?:(?:(?:[0-9A-Fa-f]{1,4}\:){1,7}|\:)\:)|(?:\:(?:\:[0-9A-Fa-f]{1,4}){1,7})|(?:(?:(?:(?:[0-9A-Fa-f]{1,4}\:){6})(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}))|(?:(?:(?:[0-9A-Fa-f]{1,4}\:){5}[0-9A-Fa-f]{1,4}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}))|(?:(?:[0-9A-Fa-f]{1,4}\:){5}\:[0-9A-Fa-f]{1,4}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,1}(?:\:[0-9A-Fa-f]{1,4}){1,4}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,2}(?:\:[0-9A-Fa-f]{1,4}){1,3}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,3}(?:\:[0-9A-Fa-f]{1,4}){1,2}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:(?:[0-9A-Fa-f]{1,4}\:){1,4}(?:\:[0-9A-Fa-f]{1,4}){1,1}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:(?:(?:[0-9A-Fa-f]{1,4}\:){1,5}|\:)\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3})|(?:\:(?:\:[0-9A-Fa-f]{1,4}){1,5}\:(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}))(?:\%\d+)?)\])$/;

p.s. it's RFC822 and RFC5322 conformant, except for the length validations which cannot be done in a single pure regex.

edited Jun 7, 2011 at 7:17

answered Jun 7, 2011 at 7:11

shinkou

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4 Comments

Awais Qarni Over a year ago

There is some double quote missing in your regex

shinkou Over a year ago

@Awais Qarni Really? Could you specify?

Awais Qarni Over a year ago

Dude I copy you regex and pasted in my javascript file all the code below it turns to blue as we often experience missing some quote. When I only put " at the end it turns normal. Thant's why I said

shinkou Over a year ago

@Awais Qarni, don't trust your editor. LOL I'm sure it works. ;) I just double checked.

Ben Roux · Accepted Answer · 2011-06-07 07:05:34Z

2

For starters, \w is equivalent to [a-zA-Z0-9_], so changing that will make your regex decidedly simpler.

/^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,4}$/

I have tried this on all of your posted emails, and it works fine

answered Jun 7, 2011 at 7:05

Ben Roux

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1 Comment

Awais Qarni Over a year ago

Hi thanks for responce. I have used your regex but it is still not validating my format [email protected] but it is validating [email protected]. Then where Am I wrong?

Awais Qarni · Accepted Answer · 2011-06-07 11:36:51Z

0

try this

/^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,4}$/

edited Jun 7, 2011 at 11:36

Awais Qarni

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answered Jun 7, 2011 at 11:12

Pratik

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