What is "www" inside a URL used for?

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Hi there,

what exactly is "www" inside a URL used for? Is it correct that one can
omit it when typing an address in a webbrowser without any negative effects?

I'm having a tough time trying to find out an answer for this question
on the internet, maybe someone here can help!


Re: What is "www" inside a URL used for?

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Traditionally I think "www" was simply to indicate that it was web that was
being referred to rather than email or some other protocol. But this was
only convention since the http bit specifies the protocol.

Whether you can omit the www depends on how the webserver and DNS has been

Mostly you can omit the www and it won't matter. For example
http://www.cryer.org.uk and http://cryer.org.uk both return the same

However, if a site wanted they could serve up different content with the www
than without. I don't know of any that do this, but its possible.

What you do need to be aware of is that not all webservers are configured
for the non-www version and equally not all DNS entries are provided to
cover the non www version. For example I use some cheap hosting (which I'm
considering moving away from) for www.cryer.co.uk, and the site's DNS is
tied up with hosting (never a good idea) and they don't provide a DNS entry
for the non-www version. So www.cryer.co.uk will resolve but cryer.co.uk

So, in summary: mostly you don't need to use the www but you do for some

Hope this helps.
Brian Cryer

Re: What is "www" inside a URL used for?

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example.com is a domain name, the thing you pay money to register.

foo.example.com is a hostname, a name that (in geneneral) refers to
one server operated by the example.com people.

mail.example.com is a name used to refer to example.com's email
server. This same server might also have the name postman-
pat.example.com and be alongside other machines in the same rack that
are called jess.example.com (that does spam log analysis) and granny-
scoggins.example.com (the host server for the Outlook clients)

You can do an awful lot of this stuff with DNS - giving machines two
names simultaneously, one that's "functional" (e.g. "mail") and one
that identifies that actual hardware (e.g. "postman-pat"). When it's
time for  a hardware upgrade, the DNS moves the "mail" hostname from
"pat" to "new-improved-pat-2" and everyone carries on working on the
new server, without having to reconfigure their email clients.

Another normal feature of working with DNS is to make the "bare"
domain name relate to one of these hostnames, to allow simpler names
to be used.

In the early '90s, TCP/IP networking, DNS and email was well
established, but the web wasn't. TCP/IP was used internally to
organisations for fileservers etc., but the only externally visible
service related to the domain name was email. So it becaome
conventional to map the bare "example.com" domain name onto the
hostname for the email servers. An email address of
fred@mail.example.com  could thus be shortened to fred@example.com

There might be a couple of other protocols in use externally too,
typically ftp, maybe telnet and rarely gopher. These used hostnames
for "ftp.example.com" etc., again just by convention rather than by
mandate. Distinctive hostnames led to simpler lives for the IT admins,
particularly where different teams were responsible for different kit.

Then the web started to happen. Slowly.  It was a toy for geeks in the
IT department, not part of business, so it didn't usually get to
disrupt this "important" email business. Web servers would appear from
recycled old servers and they'd get a hostname that would keep them
out of the way and out of trouble - by convention, this was
"www.example.com" although the odd example of w3.example.com did crop
up and even bizarre examples like the "rswww.com" domain name used by
RS components in the UK (by rights this should have been rs.co.uk)

By the mid '90s, there was serious widespread interest in the web.
This whole "www.*" business became entrenched. It was _normal_ to do
this, but it was never a standard, nor ever required.

In 1997 (AFAIR) Slashdot started to use the domain name slashdot.org
and also the hostname slashdot.org in their URLs. This was the first
mainstream(sic) site I knew of that deliberately skipped the "www.",
albeit as part of a complicated geek-joke.

Gradually people realised that it was 4 characters fewer to type. The
practice spread, but glacially slowly.

Why doesn't it cause confusion with email?  That's because TCP/IP
networking also has a notion of "ports" and port numbers. These are
implicit, so not obvious to the users, but as far as the routers and
servers see, web traffic (on port 80) is obviously different from
email (on port 25). So with a properly configured router, http://example.com
traffic goes to a whole different server from fred@example.com, just
as it ought to.

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No. If you want a site to respond to either hostname, then the site's
operator has to configure the site to do so. It's easy, but it
requires some deliberate action to do it. Many hosting operations now
so as standard.

Re: What is "www" inside a URL used for?

Scott Steiner wrote:

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The "www" was used to designate the [World Wide] Web server at that domain
(www.example.com) as versus any other server there (news.example.com;
pop.example.com; smtp.example.com ... ).  Whether or not it's omittable is
dependent on the server setup at any given domain.

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