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What's the point of having www.? Isn't it just useless extra text? Since everyone is used to it, www.google.com looks more well-balanced than google.com, but why did it start in the first place?

One thing I noticed, is that google.com has the IP of 74.125.53.100, in the UK, while www.google.com has the IP of 209.85.135.106, in the US. Could anyone explain a bit on that?

Edit: Is example.tld supposed to be a different machine than www.example.tld? Does it have to be?

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Nice question. I'm curious about abbreviating "world wide web" to something which (of course is shorter on paper/screen) is actually 3 times longer to say out loud. Maybe the only example of this in the English language. Other languages don't have this issue of course. Any good ways to simplify? –  outsideblasts Oct 24 '09 at 21:24
    
"www" usually is NOT a sub-domain--you're unlikely to see foo.www.example.com. Instead, "www" is often CNAME--an alias for some other physical machine. –  Dan Oct 24 '09 at 22:41
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Isn't a cname a type of subdomain? –  Mk12 Oct 25 '09 at 1:53
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Yes, www. is a subdomain, and it does not matter if it's got its own address (A/AAAA) records or if it's simply CNAMEd to somewhere else. It stays a subdomain. –  grawity Oct 25 '09 at 9:04
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Technically speaking, I think Dan may be correct: www would refer to a computer (a host) either directly (via an A record) or indirectly (via a CNAME record; an alias), so it would be a hostname, or a fully qualified domain name (FQDN). It could still be that subdomain is a general term for any domain name that has a parent domain though. –  Lee B Oct 25 '09 at 10:13

5 Answers 5

up vote 54 down vote accepted

Before the World Wide Web, there was still an Internet, and it was used for a variety of things: telnet, email, gopher, FTP, etc. At that time, it was traditional to assign domain name aliases to servers for common functions. So, smtp.example.com would be example.com's outbound email SMTP server, ftp.example.com would be example.com's FTP server, etc.

When the Web came along (early 1990's), it was just yet another application / protocol -- it wasn't necessarily envisioned at that time that it would be come the most popular thing to use the Internet for, next to email. So an organization's web server was assigned a domain name alias of "www." like any other service would have typically been assigned.

Over time many sites started dropping the "www.", because URLs are after all often typed in by people and yes it's 4 more characters than really necessary. But, "www." still lingers today and it's not likely to ever completely go away.

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In agreement with bm. The domain (eg google.com) handles many services and the www kind of says which service it is using (www, mail, smpt, pop, ftp...). Of course, as www traffic is probably the most common kind, servers will most likely know what is expected, and act accordingly. Many servers are configured to redirect traffic from (eg) google.com to www.google.com. One reason for this is that search engines often see google.com and www.google.com as different sites (which is bad, for reasons not relevant here). Sites leaving off the www are becoming more common eg superuser.com! –  outsideblasts Oct 25 '09 at 2:12
    
So the www means it is for the web, for the http protocol, and also to separate it from subdomains (for cookies), but now some servers (like superuser) are not using the www (although makng it redirect to the plain non-www) because they are only intended for that. –  Mk12 Oct 25 '09 at 4:16
    
@Mk12: You bring up an interesting point - the http:// protocol is intended for web traffic, whereas the other popular subdomains have their own protocols like ftp://. Are there many cases where HTTP is appropriate for non-website traffic? –  DisgruntledGoat Oct 27 '09 at 15:55
    
http is for hyper text, html. So no matter what will be received is plain html. I don't really get what you mean about 'ther\ir own protocols', ftp is the file transfer protocol. –  Mk12 Nov 3 '09 at 16:38
    
Indeed, the internet was totally unexpected in the capacity it is today. en.wikipedia.org/wiki/History_of_the_Internet –  Jeff F. Sep 9 '10 at 18:44

It could be worse. The British parts company 'RS' seems to have fundementaly misunderstood the whole thing - their website is rswww.com

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You'll be glad to know that they've "upgraded" their site address to "uk.rs-online.com/web/";. They did leave the title saying "Welcome to rswww.com" though ;D –  Lee B Dec 26 '09 at 19:49

No idea if this is traditionally why www. is used, but one possible reason:

Say you have a server which runs web, SMTP and IMAP servers. Users access the web server via www.example.com, SMTP via smtp.example.com and IMAP via imap.example.com

Your server becomes heavily loaded, so you want to split the web-server to a new machine. To do this, you simply change the "www" subdomain to point to your new web-server's IP address.

For larger internal networks, this is an easy way to move servers around.. Just change the internal SMTP server DNS entry and all clients will automatically start using the new machine. No forwarding of ports to worry about

With internet facing servers, you would probably keep both servers on the same NAT'd network, and forward port 80 to a different machine, or use a load-balancer

There are benefits to retaining the "www." part of the URL for purely web-servers, particularly with regards to cookies, as Andrew Moore and this blog.SO post explain.. Plus if you redirect the non-www domain, users don't have to type it (and even if you don't, most browsers will try "www.example.com" if "example.com" doesn't work)

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It's simply a matter of abstraction, like having bills addressed to "The Club Secretary" instead of "Susan". If you have bills sent to susan, and sales catalogs, and CVs, then what happens if you hire Bob to handle HR stuff like CVs? The mail is still addressed to Susan, and no one will know it's for Bob until Susan has found time to open it and make sure it's not meant for her. So instead of naming "Susan", the actual person, you name "Human Resource Department" -- the ROLE.

Likewise, you name computers for their ROLEs, not the actual computers. So you have a computer called www.yourcompany.com if you serve websites, and a computer called ftp.yourcompany.com if you provide an FTP service, etc. If you don't, then one computer, yourcompany.com, has to receive all the internet traffic, and then pass it on to the right place. www.yourcompany.com could be all the webservers at google, but if yourcompany.com is a laptop, the laptop will be overloaded, while the web servers will still be sitting around waiting for information to reach them. Like Susan handling all the mail initially, one computer can handle all the roles initially, but the separate computer/domain names help to separate (or consolidate) things as necessary.

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Since they are on different ports this isn't really an issue. –  Martin Beckett Nov 16 '09 at 0:23
    
@mgb: not an issue as far as you're concerned, is what you mean. Some of us care about doing things in elegant ways. –  Lee B Dec 26 '09 at 19:47
    
it's quite possible to have http over unusual ports... –  Penguat Apr 3 '13 at 14:59

It is mostly used to separate cookies from the other subdomains.

If you are going to use cookies, definitely keep the www..

You can always use an 301 redirect to redirect the short domain to the one with www., that way your users don't have to type it.

This will allow you to create sub-domains that are cookie-less for static data serving. Without a www., cookies are served on all sub-domains. Therefore, if you are not using the www., you need a completely separate domain name to have a cookie-less domain versus just using a sub-domain.

Other than that, choosing between keeping the www. or not is just a question on which one you prefer. Just make sure to redirect the one not chosen to the other one using a 301 redirect.

EDIT:

To explain, setting a cookie uses a hierarchy for how the cookie is propagated to domain.

For example, setting a cookie to example.com effectively allows the transfer of cookies to:

example.com
www.example.com
sub.www.example.com
my.example.com
oh.my.example.com
images.example.com
hello.example.com

Versus setting a cookie to www.example.com only allows the cookie in those situations:

www.example.com
sub.www.example.com

By using a www. you are allowing yourself to use sub-domains to have different cookies from the main site (and none at all if so desired).

Without www. (or another sub-domain), all cookies set on the domain will propagate to the sub-domains.

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Huh? www. was in use before cookies existed -- from the dawn of the web in fact -- as far as I know. –  Lee B Oct 24 '09 at 22:10
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Yup, but now it’s a decent convention for keeping cookies separate if you end up using subdomains for separate sites. –  Paul D. Waite Oct 24 '09 at 23:48
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@Lee B: Because today, this is the only real reason why people keep using www. on new websites. There is no other technical reason why www. is still in use today. –  Andrew Moore Oct 25 '09 at 14:33
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Sorry, disagree. –  Lee B Dec 26 '09 at 19:46
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@LeeB. Andrew is correct, this is the only technical reason why a new website creator will choose having www over not having it. –  Pacerier Jun 26 '12 at 1:29

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