We could define Wappalyzer by saying it is an add-on for Firefox that can be used to analyze any site that you come across, and get a rundown of the different Web technologies that have been employed to put it together. As it stands right now, Wappalyzer can detect both CMS and e-commerce systems, as well as database managers and issue trackers.
The full list of tracked applications can actually be read on the site, and the number is getting close to 150.
Using a service like this one you will be able to discover the way in which your competitors have built up their sites, and which information they are getting from users. Taking that knowledge as the starting point, you will be capable of emulating what they are doing (if you feel that their sites are better than yours), or take a different approach to the one that they are taking and use technologies that are different from those that they are currently employing. And Wappalyzer can be used at no cost, too – the download link is featured on the main page.
Wappalyzer.com In Their Own Words
“Wappalyzer is an add-on for Firefox that uncovers the technologies used on websites. It detects CMS and e-commerce systems, message boards, JavaScript frameworks, hosting panels, analytics tools and more.”
Why Wappalyzer.com It Might Be A Killer
It will let you have a sharp and clear understanding of the way in which web technologies are used in practice.
Some Questions About Wappalyzer.com
How often are new applications added to the list of tracked ones? 
