How are unique visitors to a website calculated ?

Hello,

Please tell me how Google calculates unique visitors to a website ?

Thanks in advance.

 

Using their IP address I suppose.

 

yes, it must be storing the IP of each visit

 

storing IP address only is useless, since considerable amount of users share same ip, be it proxy, their office gateway or corporate firewall.
most probably the answer has something to do with cookies....

 

It could be tracked by MAC Addresses, but I dont know.

 

no, you dont know.

 

well i think Firefox clears all cookies on exit by default, meaning creating new "absolute unique user" every time someone closes the browser between site revisits

 

It is by cookies - GA is essentially a package that uses cookies to track - http://www.google.com/support/analytics/bin/answer.py?hl=en&answer=55614
As that article says - no package can be 100% accurate, a cookie based package has it's faults in that people may clear cookies, but an IP based tracking system can't track dynamic IPs properly - this also explains why people get higher numbers from awstats etc. If you've ever used a program that does use IP tracking, and looked in detail at it, you'll see that anyone using AOL has a changing IP that makes a complete mess of your stats

 

I dont think Firefox cleans cookies on shutdown by default.
And who would close the browser that frequently, I think most of people would close browser only on computer shutdown.

I am sure GA uses combination of IP, cookies, User-Agent and may be even more parameters to count uniques.

 

it will be calculated by IP address or you can take a help from Google Analytic tool.

 

Look, I even gave you the specific link to the page where they categorically say it's cookie, not IP based - here it is again
http://www.google.com/support/analytics/bin/answer.py?hl=en&answer=55614

Why are there people are DP who just join a thread to parade their ignorance, when the source to the actual answer has been given already?

 

here is more information thankyou

 

coz they just want to advertise links in their signatures/increase post count/pretend being smart to feel better for them selves?
(just like the poster directly above))

 

Closing your browser a few times a day is a great idea from many security standpoints. Especially if you do any sort of online banking and super sensitive work online.

 

while it is a great idea, not many people closing the browser, heh , most people that surf the net dont even familiar with the notion, if you ask them what browser they are using they will tell they using Google