Do you have a website, and you want to see what other sites your visitors are viewing? Well, now you can. Spyjax has created a line of Javascript that when added to any webpage it can view the visitors browsing history, essentially grabbing a couple hundred links instantly, without slowing down the page.
Though, it can not see all the visitors´ history. There are some limitations. The webpage owner can create a list of other sites, and when viewing visitors´ history, the program can see only if a site from the list has been visited.
Spyjax In Their Own Words
“Spyjax records the browsing history of website visitors. You can quickly add it to any web page with one line of HTML and start spying.”
Why Spyjax It Might Be A Killer
This program can be an extremely useful tool for companies who are interested in finding out more information about their competitors. For example, if an e-commerce site wants to see why sales are decreasing, it can see where other users are going, and therefore learn more from their competition.
Some Questions About Spyjax
Will web browsers ever be able to block the line of Javascript, without having to manually delete browsing history, or disabling Javascript? 
