A Blessing or a Curse?
Molly E. Holzschlag, Communications Director
World Organization of Webmasters
can be used for many reasons, some legitimate, some
not so. Uncover the benefits and pitfalls
of this 'dark practice' of web design and you might
find cloaking is the perfect solution to enhance
A Blessing or a Curse?
As soon as you mention the idea of page cloaking
you can be sure that someone somewhere is going
to jump to the conclusion that you intend to cheat
the search engines. There is no denying the fact
that search engine spammers have used page cloaking
in the past, and that the reputation of cloaking
has been damaged as a result. The fact remains however
that there are still many legitimate reasons for
wanting to dabble in various forms of page cloaking,
so don't be too quick to judge!
What is Page Cloaking
Page cloaking is the practice of altering contents
of a page depending on the software, method and/or
IP address being used to access it. Cloaking has
been made possible through the use of server side
technologies such as ASP and PHP (amongst others),
and has been abused so much in the past that it
will probably never shake off it's bad reputation.
Cloaking is used in all manor of situations, some
of them you won't even be aware of until it is pointed
out to you. I'll admit to using it on my own site,
and I'm not ashamed of the fact either!
There are several different ways of implementing
cloaking; each is based on the environment variables
that are passed to the server as part of the actual
What browser/program is making the request? (HTTP_USER-AGENT)
What IP address are they trying to connect from?
What page (if any) did they come from? (HTTP_REFERER)
Did they recently request a page? Have they already
set preferences? (Session data)
While the environment variables available to us
can be used independently to make generalisations
and educated guesses, they become powerful customisation
tools when combined.
By identifying the program used to make the request,
we get an idea of how the data will be used and
the capabilities of the browser. Suddenly we can
use specialised page designs without having to use
or redirect users to different URLs depending on
what they could handle. It can also prove an effective
way to reduce needless data transfer costs; by sending
only the code the browser or bot will understand.
When we want to target groups of users based on
their geographical location or connection speed,
we can use IP addresses to make an educated guess.
Different ISPs will own different IP blocks; these
ISPs may operate in a specific region or offer only
broadband services. While gathering and maintaining
current IP data can be a chore, it is probably the
best way to get information on the location of the
user without specifically asking them.
The use of referral or session data is probably
the most interesting area of cloaking however, as
this is where we can learn more about the person
making the request. With a little research, you
can match visitor types by the sites they come from
and tailor the site to their needs. Referral and
session data can tell us a lot about the visitor
without actually needing to identify them; the possibilities
are limited only by the imagination!
Why Use Cloaking?
There are many different reasons why people want
to use page cloaking, and while some of these can
be devious in nature, others are designed to be
helpful or to standardise the user experience. Some
reasons for using page cloaking include:
• To serve known
search engine bots with content optimised for best
• To hide the
real keywords and text used for rankings from normal
• To alter the
identity of the site depending on who accessed it.
• To protect
the server and it's contents from malicious bots
• To re-brand
shared content depending on the domain name used
to access it.
• To limit the
options available depending on browser features
• To iron out
• To serve relevant
information to the user based on Operating System
• To create a
more personalised experience for the visitor.
You see page cloaking is perhaps more common than
you first think, and when you look at the whole
picture it doesn't seem as bad as some people make
it out to be. It's not so much whether or not you
use it, but rather how you use it.
I use ASP and dynamically edit the page to show
the style sheet optimised for the browser. Even
though my server changes just one line from one
browser to the next, it is technically page cloaking;
the style sheet it serves to the visitor using Opera
is not the same style sheet it sends to the visitor
using Internet Explorer. Ironically, if I chose
to use a script on the client side to do the same
thing, it would not be considered to be page cloaking!
So why does it matter where the script is executed
if they both do the same thing?
It's all because we can look at the source code
of the script when it is on the client side; thus
we can see the alternatives that are available simply
by looking at the way the script works. On the server
side however, all the logic is hidden away in some
script or server module and we only see the results
of the server's decision; not how it came to the
conclusion on how it should respond to the request.
The Dark Side of Cloaking
The use of cloaking is controversial because of
the way it has been abused in the past. Some search
engine optimisers use it in their promotional campaigns
to serve pages optimised for each of the search
engines. While this may seem unfair to other site
owners fighting for rankings with the same keywords,
some of the arguments for doing so are certainly
• Why increase
the visitors download time by including Meta tags
they don't normally see?
• Why send images
to the search engines when all they really look
at is the text?
• Why should
they share keyword lists they spend the time researching?
All the reasons above may seem rather selfish, but
just because a Webmaster wants to minimise their
data transfer costs and protect the investment of
their time and effort does not make them an unethical
person. Only when the topic of the alternative pages
strays from the page the visitor sees can the practice
of optimising for the search engines in this way
be deemed to be unethical. There is a fine line
between optimising a page for the search engines
and misleading them altogether!
Page jacking occurs when a site owner takes the
source code of a page that performs well in the
search engines and cloaks it behind their own site.
If this is done properly, a search engine spider
will see the optimised page and do one of two things;
improve the ranking of the unrelated site, or remove
the original site from their indexes. This unethical
use of cloaking is unfortunately difficult to spot,
and is one of the reasons why the use of cloaking
is so controversial.
Is Cloaking all that
Lets forget for a moment the role and ethics of
using cloaking for promotion and concentrate on
the human factor. After all the main interest of
any site owner should be the thoughts and feelings
of their visitors.
Given the choice, I'm sure you would like to make
your web site more intelligent. Does this particular
visitor use a Mac or a PC? Opera, Netscape or Internet
Explorer? Why should you waste the user's time by
asking them for information that is readily available
by the way their browser identifies itself? Wouldn't
it be easier to just establish how best to optimise
the page source code for the user's browser and
operating system before they get it?
By establishing details from the user agent string
and determining IP addresses, it is also possible
to make an educated guess at the best default language
or localised settings. It would be far more convenient
if your visitors didn't need to convert the prices
into their own currency or search through a long
list of international branches to find their nearest
Although the examples used above describe the use
of program identification and IP address to customise
the user experience, user-friendly cloaking scripts
can also make use of things such as referrer and
session data. Knowing that a visitor came from a
search engine while looking for a particular keyword
gives you a great opportunity to optimise the page
for better conversions. This can even work for informational
sites; if they came to that page looking for information,
there is a chance that they might be interested
in buying a book on the subject!
Cloaking could also be used to protect yourself,
your site and your visitors in a variety of ways.
For example, it can be used to:
• Ban IPs of
known email harvesters (useful if you run a community
• Minimise the
damage and cost of bots flooding the server.
• Filter out
questionable content from visitors that enter from
a child oriented site.
• Limit access
by countries that require it by law or who are likely
to find the site content objectionable.
• Disable site
features such as order forms to those surfing from
problem IP addresses or countries thought to be
involved with fraud.
Such legitimate uses of cloaking ought not to be
penalised by the search engines. However the activities
of site owners that optimise for the engines have
meant that those that dare to implement such features
to their site run the risk of being banned by the
The Future Could Be
The use of cloaking is sure to become more commonplace
as time goes on. Not everyone will hold back on
implementing features that improve the usability
of their site just because they are worried they
will be banned by the search engines.
It would be sad to see the legitimate use of cloaking
thwarted by the minority of site owners who choose
to use it purely to achieve higher rankings through
deception. Cloaking has the scope to make sites
seem far more intelligent than they are, to the
point where it becomes invisible to the vast majority
of people who visit the site that use it.
Wouldn't it be nice to make a visitor feel more
"at home" on your site the first time
they visit it? Or to provide alternatives to those
with limited access so they don't have to miss out
Cloaking can make such features a reality. If we
are willing to let it!
Deemed one of the Top 25 Most Influential Women
on the Web, there is little doubt that in the
world of Web design and development, Molly E.
Holzschlag is one of the most vibrant and influential
people around. With over 25 Web development
book titles to her credit, Molly currently serves
as Communications Director for the World Organization
As a steering committee member for the Web Standards
Project (WaSP), Molly works along with a group
of other dedicated Web developers and designers
to promote W3C recommendations. She also teaches
Webmaster courses for the University of Arizona,
University of Phoenix, and Pima Community College.
She wrote the very popular column, Integrated
Design, for Web Techniques Magazine for the
last three years of its life, and spent a year
as Executive Editor of WebReview.com.
Find Molly's Web Site at www.molly.com.
Molly Holzschlag can be contacted by emailing
her at email@example.com.
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