Difference between Alexa, Google Analytics, Quantcast and Compete website statistics

Question

I am getting confused by the following traffic metric systems: Google Analytics, Alexa, Quantcast and Compete metrics because they each show different values. ie. unique traffic, visits, pageviews, etc. Which among them would be the most reliable and why does each show different values.

Solution 1

Google Analytics would be the most reliable.

Edit

I was being a bit lazy for not posting this, earlier, I realize that this comparison might help others (including myself!)

All the services you mentioned offer javascript code based tracking. Alexa also does this in their Pro Plan, so do Quantcast and Compete. However, the data reported by all these services is not accurate.

This has been reported by SEOmoz in an extremely neat fashion, Compete and Alexa have been scoffed at in TechCrunch.

A non-biased version is provided by Avinash Kaushik on the differences between these and other systems. I would highly encourage you to go through this post, because I cannot explain things as clearly and as indepth as this man. He rocks!

In short, if you want to measure metrics about only your site, then Google Analytics is the best tool (I could be biased since I have been using this for the past 3 years on a daily basis and am generally able to find answers about data discrepancies if any).

Do note that GA does not provide competitor data, where as some of the other systems do. You can find such data using Google Trends for Websites. Do read a longer post on KISSMetrics on this.

Solution 2

Google Analytics measures your traffic on your own site through a Javascript snippet integrated into all your website's pages.

Alexa, Compete and Quantcast merely do estimates of your traffic and are generally not very reliable. Not sure about Alexa and Compete, but Quantcase does offer to integrate a javascript snippet of their own, which increases reliability of the measurement.

If you really need to know your traffic as accurate as possible:

Make sure you have Google Analytics integrated and running on all your pages or even better: Install some serverside tracking.

Comments

[MrWhite]

From the stats services mentioned this might be correct, but why?

[David K.]

Because Google Analytics is usually not estimated (to a degree), but the traffic is counted and sent to Google's servers through your own tracking snippet.

[Simon Hayter]

DKOATED that's correct but I'm sure w3d is fully aware of this and indicating that @Prasad should be answering with more detail in why for the sake of people not knowing :P

[Prasad Ajinkya]

I should have answered that in more detail, the way @DKOATED has done, I apologize for that temporary lapse in laziness. Posting a detailed answer ... turns out that the simple answer can require a fairly lengthy reasoning!