Email address validation, again

Question

Looking at the posts here for email address validation, I am looking to be much more liberal about the client side test I am performing.

The closest I have seen so far is:

^([\w-\.]+)@((\[[0–9]{1,3}\.[0–9]{1,3}\.[0–9]{1,3}\.)|(([\w-]+\.)+))
([a-zA-Z]{2,4}|[0–9]{1,3})(\]?)$

That will not match this#[email protected], which according to RFC is valid

Uppercase and lowercase English letters (a-z, A-Z)
Digits 0 through 9
Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~
Character . (dot, period, full stop) provided that it is not the first or last character, and provided also that it does not appear two or more times consecutively.

I want a pretty simple match:

Does not start with .
Any character allowed up to the @
Any character allowed after the @
No consecutive . or @ allowed
Part after the last . (tld) must be [a-z0-9-]

I will use \i to make the search case insensitive. The consecutive characters is where I am getting hung up on.

I have been working on one, looks like this is going to cover it broadly .+@(?:[-a-z0-9]+\.)+[a-z]{2,10} I do not suppose there will be a tld longer than 10 chars, .museum seems to be the current record holder in strangeness. — user170579
– user170579, Commented Sep 22, 2009 at 1:51
possible duplicate of How to validate an email address in PHP (see the regex pattern in there) — PeeHaa
– PeeHaa, Commented Aug 8, 2013 at 9:35

Esteban Küber · Accepted Answer · 2009-09-22 00:51:55Z

4

If you want to match against the official standard, you can use

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

So even when following official standards, there are still trade-offs to be made. Don't blindly copy regular expressions from online libraries or discussion forums. Always test them on your own data and with your own applications.

answered Sep 22, 2009 at 0:51

Esteban Küber

37k15 gold badges82 silver badges97 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Matthew Scharley · Accepted Answer · 2009-09-22 01:52:13Z

1

/^[^.].*@(?:[-a-z0-9]+\.)+[-a-z0-9]+$/

edited Sep 22, 2009 at 1:52

answered Sep 22, 2009 at 0:33

Matthew Scharley

133k55 gold badges199 silver badges225 bronze badges

2 Comments

user170579 Over a year ago

Seems near perfect, one exception: <pre>[email protected] [email protected] [email protected] [email protected] t#[email protected] t#est@exa#mple.com <-this matches t#est@exa#mple.c#om</pre> Anything after the last @ should be only [a-z0-9-] (valid domain chars) then a dot, then another [a-z0-9-]

Matthew Scharley Over a year ago

In your question, you said only the TLD name should be [-a-z0-9]. Fixing that is trivial.

brianegge · Accepted Answer · 2009-09-22 01:24:50Z

0

It depends on who is using your applications. For internal applications, often a username is a valid email address. Much of the RFC-822 email spec describes additional fields which may be present in an email address. For example, Allen Town , is a pretty standard email address which you might type into your favorite mail client. However, for an application, you may want to be the one adding the name to the email address when you send email, and don't want that to be part of the users address.

The most liberal way of validating an email address is to just attempt to send an email to whatever address the user gives. If they receive the email, and can confirm it, then it's a valid address.

answered Sep 22, 2009 at 1:24

brianegge

30k13 gold badges77 silver badges103 bronze badges

1 Comment

user170579 Over a year ago

I understand this, but I would like some up front validation. Just so the aol users can not make mistakes :) There will be no local delivery, so the email must be in the format of [email protected]

Loki Astari · Accepted Answer · 2011-05-12 15:55:53Z

0

function validator(email) {
   var bademail = false;
   bademail = (email.indexOf(".") == 0) ? true : bademail;
   bademail = (email.indexOf("..") != -1) ? true : bademail;
   bademail = (email.indexOf("@@") != -1) ? true : bademail;
   if(!bademail) {
      var tldTest = new RegExp("[a-z0-9-]");
      var lastperiodpos = email.lastIndexOf(".");
      var tldstr = email.slice(lastperiodpos + 1);
      bademail = (!(tldTest.test(tldstr))) ? true : bademail;
   } 
   return bademail;
}

edited May 12, 2011 at 15:55

Loki Astari

267k87 gold badges344 silver badges575 bronze badges

answered Sep 22, 2009 at 1:07

Anthony

37.2k26 gold badges103 silver badges167 bronze badges

5 Comments

TrueWill Over a year ago

+1 because some boor gave you a -1 without leaving a comment. I hate that!

Anthony Over a year ago

Thanks. I just figured I'd actually keep it simple, as requested, rather than involve regex where it's not needed. Wish I could have thought of a way to use it at the end that wasn't convoluted.

pvorb Over a year ago

-1. I don’t think, that ".." is generally illegal in an email address. A friend of mine once had such an email address. You should simply remove that rule. And what about special characters in the domain part? They are also allowed, but must be translated according to RFC 3492. So this is not a correct answer.

Eric J. Over a year ago

@pvorb: You are wrong... ".." (consecutive dots) is generally illegal in both the local part and domain part of the address. en.wikipedia.org/wiki/E-mail_address#Local_part

pvorb Over a year ago

@EricJ.: Tanks for clarification. It seems like I and the email provider of my friend have been wrong.

Steen · Accepted Answer · 2012-12-10 11:57:24Z

0

A very Perl-ish RFC822 compliant regular expression can be found here

answered Dec 10, 2012 at 11:57

Steen

6,8973 gold badges41 silver badges56 bronze badges

Comments

Roy M J · Accepted Answer · 2013-08-08 09:26:22Z

0

The following has been useful for me for quite sometime now.

function validateEmail(email) { 
    var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return re.test(email);
}

answered Aug 8, 2013 at 9:26

Roy M J

6,9367 gold badges54 silver badges79 bronze badges

Comments

Ain Tohvri · Accepted Answer · 2012-04-03 12:56:36Z

-1

Perfect validation regex is probably hard to match, but I've used this one for quite some time:

/^([\w-\.\+])+\@([\w-]+\.)+([\w]{2,6})+$/

Only changed it recently to match 6-char TLDs.

answered Apr 3, 2012 at 12:56

Ain Tohvri

3,0356 gold badges34 silver badges51 bronze badges

1 Comment

PeeHaa Over a year ago

What about 7-x char TLDs or quoted strings?

Collectives™ on Stack Overflow

Email address validation, again

7 Answers 7

Comments

2 Comments

1 Comment

5 Comments

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

Comments

2 Comments

1 Comment

5 Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related