The four parts of a This presentation is on URLs. URL sounds
URL exotic – it stands for universal resource locator
URLs – uniform resource locators
– but it is just a geek term for a Web address. A
IT skills: compose URLs URL is the address of a resource on the Web.
IT concepts: parts of a URL, shortened URLs,
domain names, directories, file names
You’ve typed URLs into Web browsers many
times, but may not have thought about the
meanings of each of the four parts of a URL.
We will review them and also mention
This work is licensed under a Creative Commons Attribution-Noncommercial-
Share Alike 3.0 License.
In order to understand the parts of a URL, we
will also cover domain names, directories and
Communication URLs are a technical topic, but understanding
Where does this topic fit? them will also help you use the Web, so we
• Internet concepts
include this presentation at two places in our
– Applications class outline.
• Internet skills
– Application development
– Content creation
– User skills
URL – a Web To retrieve a page from a Web site, you type its
URL, uniform resource locator
address URL into the box at the top of the browser and
hit enter. The browser then retrieves the page
from the server and displays it. URL is just a
fancy way to say the Web address of the page.
In this example, a short professional biography
Client Server that is stored at the listed URL is retrieved and
The four parts of a If you look at URLs, you see that they can be
URl Four parts of the URL broken down into four parts. Note that some of
the parts may be omitted at times – we’ll talk
about that later. For now, let’s take a look at
http://som.csudh.edu/fac/lpress/shortbio.htm each of the four parts.
Part 1 – this is a The URL prefix “http://” indicates that this is
Web page http:// the locator for a Web document that should be
retrieved and displayed. It turns out that Web
browsers can also function as clients for other
http://som.csudh.edu/fac/lpress/shortbio.htm services like file transfer, but that is seldom
done. For that reason, one can often omit the
“http://” since most browsers will plug it in for
Part 2 – the domain The next part of our example URL reads
name of the server The domain name “som.csudh.edu”. That is the domain name of
the server. Domain name is another fancy geek
word – it is the name of the computer the server
program is running on. We will say more about
domain names in another presentation. For
now, it’s enough to say that the domain name
identifies a unique computer on the Internet.
Part 3 – the The next part of the URL is the directory or
directory the page is folder containing the page we are looking for.
in on the server http://som.csudh.edu/fac/lpress/shortbio.htm
Every computer has many files in storage. We
would quickly become confused in trying to
root locate a single file in a list of say 100,000
names. For that reason, we organize our storage
staff fac admin into hierarchical directories, sub-directories,
sub-sub-directories and so forth.
* lpress jsmith ... jdoe
Here we have three sub-directories – for staff,
faculty and administrators. Since I am a faculty
member, my directory, named “lpress,” is a
subdirectory of the fac directory. Each faculty
member – jsmith, jdoe, and the rest would have
directories in the fac directory.
Part 4 – the name of The final part of the URL is the name of the file
The file name
the file on the server we wish to retrieve, in this case “shortbio.htm.”
http://som.csudh.edu/fac/lpress/shortbio.htm Since shortbio.htm is in the lpress directory, the
Web server will send that file back to the client,
which will display it. The user can then read
my short biography.
staff fac admin
Note that the file name has two parts separated
lpress jsmith jdoe
by a dot. The suffix or “extension” indicates
what type of file it is. The suffix “htm” means
that this is an HTML file, in other words a Web
page. (We will say more about HTML later).
Shortened URLs Let’s look at a couple more things concerning
URLs may be shortened URLs.
shtml#apply_for_scholarships For a start, you can save space by shortening a
URL. If you try them out, you will see that both
http://bit.ly/djeREW of the links shown here are to the same page.
There are many URL shortening services on the
Internet. I used one called bit.ly to create this
(I shortened the URL using the service at http://bit.ly. There
are others that do the same thing.)
Shortened URLs can Be cautious when clicking on shortened URLs.
be risky. Know the source of a shortened URL
Shortened URLs hide the actual domain name,
so you cannot tell where they link to by looking
Click the link shown here to see why you
should only go to shortened URLs from trusted
Most Web clients As mentioned previously, if you delete the
assume http:// by You can delete the http:// http://, the client will assume the message is for
default a Web server and request the page as if the
http:// had been included.
Default file names If you delete the file name, the Web server will
You can delete the file name look for a file with a default name, which is
specified by the server administrator.
Traditional default names are index.htm,
Index.html, default.htm, and default.html.
The Web server will look for a file with a default name, which
is specified by the server administrator.
Traditional default names are index.htm, Index.html,
default.htm, and default.html.
Summary Here we summarize the meaning of the four
parts of a URL. In addition to learning about
the parts of a URL, we saw that they may be
shortened using a service like Bit.ly and that
This request is for a Web (http) server some parts of the URL were optional.
The server program is running on a computer with the domain
Look in a subdirectory called fac/lpress
If there is a file called shortbio.htm, send it back to the client to
We also learned about domain names,
be displayed; if not, send an error message back to the client directories and file names.
Domain name = the unique name of a computer on the Internet
1. Without looking back, can you describe the four parts of a URL
and explain what each means?
2. What happens if you misspell the file name in a URL?
3. What happens if you misspell the domain name in a URL?
4. Can you omit the domain name?
5. What happens if a URL shortening service like bit.ly goes out