I was searching for understanding what is the “www” at the beginning of so many web addresses in the Internet. I read in somewhere that “www” is called “hostname”.
The world “hostname” made me go a step further in searching, I read so many threads and articles but I am still confused about that.
So I decided to ask some related questions here to make it clear and I need solid and comprehensive answers please.
-
“hostname” vs. computer name: Is the “hostname” the same as the computer name, if its true, suppose that my computer is a web server and my computer name is “Robin” so is it correct to conclude that a hypothetical web site would be something like:
Robin.websitename.com
? -
“hostname” vs. subdomain: If “mail” in
mail.google.com
and “developers” indevelopers.google.com
are called subdomains why isen
inen.wikipedia.org
called hostname? What is the difference between host name and subdomain? -
What is the relation between host name and fully qualified domain name (FQDN)?
-
What is the “www” in URL of some web sites? As you know Google’s web address is
www.google.com
but we have many web sites without “www” for example:superuser.com
anden.wikipedia.org
. I read in this article that “www” is just a declarative thing not more and is not related to the concept of hostname. Do you verify that?
Best Answer
The best way to explain the differences between these different items—that are related but different—is to break it down by example. Think of networks like a tree:
The “trunk” and “branches” are “domains” and “subdomains” and the leaves are individual devices, like computers. So let’s start there.
A “computer name” is strictly a local convention: I have a computer named
jakegould
. This computer name is simply the name I have assigned my local machine. Nobody outside of my LAN will know this computer name; this is strictly a local setting.A “hostname” (aka “nodename”) is a network identifier: If I wanted to publicly advertise my local computer to others, I would have to attach a “hostname” to the IP address of my computer. The “hostname” doesn’t really have to have anything to do with the computer name, but many times administrators like to use the same name to make things easier to understand. Also a “hostname” doesn’t always mean the computer is exposed to the Internet; it’s just an easy way to let others on your network where/what your computer is. As Wikipedia explains; emphasis is mine:
A fully qualified domain name (FQDN) is just that; a fully qualified domain name: Now that might seem confusing but you need to think of it this way: It just means in the great scheme of things, what is the actual “path” to get to a computer. So let’s say I have my computer named
jakegould
and it has a hostname on my LAN that isjakegould
. Within the context of my LAN, thatjakegould
is my computer name, and is my “hostname” and can possibly be considered my “fully qualified domain name” depending on my LAN architecture. Meaning let’s say my office LAN has other nodes in it like,first_floor
andsecond_floor
and my “hostname” ofjakegould
is on thesecond_floor
network. Well, if that were the case, then my LAN-based “fully qualified domain name” would bejakegould.second_floor
and that is it. But let’s say I worked at a big company named “big_company.com” and my computer were somehow exposed to the world. Then in that case, my WAN-based “fully qualified domain name” could bejakegould.second_floor.big_company.com
or maybe even justjakegould.big_company.com
if the network administrator didn’t want to be hassled with the “second_floor” designation. Again, as Wikipedia explains; emphasis is mine:The “www” in some website names is a “hostname” designation that is historical in nature: Basically, back in the 1990s when the world wide web was still in it’s infancy, networks had many different services attached to them. And mainly in an academic context. So there would be a place like
whattsamattau.edu
and that school would have FTP services onftp.whattsamattau.edu
, email onmail.whattsamattau.edu
and so on… So when the world wide web came along, they would just have placed the web server onwww.whattsamattau.edu
. Nowadays, everyone—and seemingly everything in the world—has a website. And many people just register domains just for the web service. So the historic convention ofwww
is discarded in many cases. Many people have websites withoutwww
but will still have accommodations to redirectwww
traffic to the main, non-www
hostname. But technically speaking,www
can still be considered a hostname.BONUS (Never Asked But Mentioned/Implied): What is a “subdomain” in the great scheme of things: A subdomain is basically just a child of a parent domain/hostname. So in my example of
jakegould.big_company.com
thejakegould
can be considered a subdomain ofbig_company.com
andbig_company
in that can be considered to be the “domain” with.com
being the top-level domain (TLD). Yet again, as Wikipedia explains; emphasis is mine:Now after drafting all of this, it can be confusing. Many computer names are hostnames are fully-qualified domain names and in some cases they could be subdomains. It’s all a matter of context. And looking at articles online the words “domain,” “host” and “node” are used fairly loose and fast all over the place. So in my opinion, many uses of these terms are synonymous.
Which also helps to explain your confusion in item number 2:
The
en.wikipedia.org
is a subdomain and a hostname. Theen
in theen.wikipedia.org
is a subdomain of the domain namewikipedia.org
. Anden.wikipedia.org
is in itself a hostname sinceen.wikipedia.org
has an IP address connected to it and thus a computer connected to that IP address as well. Meaning theen
itself is semantically considered a subdomain, but it is also a hostname because there is a host (computer) connected to the IP address connected toen.wikipedia.org
. So knowing thatmail.google.com
anddevelopers.google.com
are hostnames as well which are both subdomains ofgoogle.com
.To possibly make things clearer think of it like this; let’s use the non-existant subdomain
fakename.wikipedia.org
as an example:org
infakename.wikipedia.org
is a top-level domain (TLD). As a top-level domain it does not resolve to an IP address. Thus it is not a hostname. It is simply a naming convention.wikipedia.org
infakename.wikipedia.org
is a domain name and it has the potential to be a hostname as well if it is connected to an IP address and resolves to a computer when one goes towikipedia.org
.fakename
infakename.wikipedia.org
is a subdomain name since it is a child domain ofwikipedia.org
in the context of the domain name itself. It can be a hostname if it connected to an IP address and resolves to a computer when one goes tofakename.wikipedia.org
.If you ping
fakename.wikipedia.org
you are attempting to ping thefakename
subdomain ofwikipedia.org
. If that ping dies—which it most likely will since it is fake—that means that the host is down or it does not exist. If it dies with an IP address connected to it, that would mean the hostnamefakename.wikipedia.org
is down. If the ping dies with 100% no IP address connected to it, them it would mean that the subdomainfakename.wikipedia.org
is an invalid hostname.Yes, this can all be confusing. But what it boils down to is the difference between what a domain/subdomain is in the context of DNS entries versus what domain/subdomain is in the context of having a host/computer connected to it.
So if this all started with your curiosity about
www
, that is a historic hostname/nodename/subdomain that is not really used as a convention as much anymore but is still so commonly used that many sites have some accommodations in place to “catch” requests towww
and redirect them to the main hostname of a website.