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Whats the purpose of the WWW subdomain?

I read about sub domains at w3schools, but Wikipedia says something different. The w3schools gave the example of www being a sub domain. Is the www before the website the subdomain or the subaddress inside a domain (as wikipedia mentioned)?

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marked as duplicate by Sathya, grawity, BinaryMisfit Nov 26 '10 at 18:31

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

up vote 10 down vote accepted

To add to that the reason many sites use the www. subdomain is that it allows for simple segregation in the file structure of the site. Everything in the www folder (and at the domain) is directly related to serving the site to the public. This allows for simple root level site organization so you could also have a dev folder and have a subdomain for your development site, and so on.

Now you not only know that it is in fact a subdomain, but also why.

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So why – Fahad Uddin Nov 26 '10 at 10:37
@farad: Don't listen to that fringe-group site. There are many reasons to continue using www, and no meaningful reason not to. For example, in advertising, a web address is much clearer to most people when it begins with www. – paradroid Nov 26 '10 at 10:51
why doesnt this site uses www then? – Fahad Uddin Nov 26 '10 at 11:09
@fahad: Because they probably felt like they didn't need it. It's a choice, but evangelising not using www seems stupid, as there are many sites that would want to use a domain name for different hosts and protocols. – paradroid Nov 26 '10 at 11:20
I never knew this. I always imagined the domain was part of the www, not the other way around. It is like there are gazillions of www's, not one. Weird. – Benjamin Mar 29 '13 at 20:04

Both articles are saying exactly the same thing. -> domain -> subdomain

The foo is inseparable from the rest of the hostname (except when dealing with search domains, but that's a completely different topic).

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and what about the www being a subdomain? – Fahad Uddin Nov 26 '10 at 7:42
Have you read my answer? – Ignacio Vazquez-Abrams Nov 26 '10 at 7:45
@fahad, yes, www is a subdomain as well. So, for the site, www is the subdomain of the domain – nhinkle Nov 26 '10 at 8:00
www is also a hostname, whereas subdomains are not always hostnames, as they are not the same thing, but www is always a hostname. – paradroid Nov 26 '10 at 10:37
@Ignacio : I did not understood the foo in your answer – Fahad Uddin Nov 26 '10 at 10:38

A sub domain normally denotes separate content from the main website.

For example, if I go to, I expect a different set of content from

The www prefix is subtly different to a sub-domain. This is actually a canonical alias that normally points to the same content as the non www prefix.

So in real-world terms, "www" is not really a sub-domain as it does not contain a "sub section" of the website. Here are some examples... or - the root of the website - a sub-domain of the website

Part Two... should you use "www" prefix?

The answer to this question is "it depends". If your audience is the "general public", you'll find that they are more comfortable starting a web address with www. If you are dealing with savvy technical types, you can ommit the www - so you'll find Stack Overflow, Super User, jQuery and many other websites with technical audiences using the non-www address as their preferred URL. Also note, though, that if you type in the www by accident, you still get to the same page!

In short, "www" isn't really a sub-domain, it's an alias and you should use it if it is appropriate to your audience.

If you are thinking about this kind of stuff, you might find the W3C Style Guidelines a useful read!

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Technically, www. certainly is a subdomain. On many sites, it's an exact copy of the bare domain, but this is not necessarily the case. – TRiG Nov 26 '10 at 15:49
+1 for canonical aliases! This is correct in a lot of standard usage cases and clears up the fact that you don't "need" a subdomain to serve at www. – David Maguire Nov 27 '10 at 4:51

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