Firefox's Tracking Protection feature, which blacklists the downloading of tracking cookies, reduces the loading time of the world's 200 largest websites by an average of 44 percent, according to a study carried out by a former Mozilla engineer.

Tracking Protection, which has been available since the release of Firefox 35 in January, is turned off by default. It is somewhat the spiritual successor of Do Not Track, but a whole lot more aggressive. Where Do Not Track asks the remote website to not send any tracking cookies, Tracking Protection prevents the local browser from making the HTTP requests for those tracking cookies. Do Not Track is optional; Tracking Protection is based off a big, regularly updated blacklist of domains that perform third-party tracking.

The study (PDF), carried out by Georgios Kontaxis of Columbia University and Monica Chew who recently left Mozilla, discusses the effects of turning Tracking Protection on. Using the top 200 websites (as identified by Alexa) as a data set, Chew and Kontaxis found that Tracking Protection reduced the number of HTTP cookies by 67.5 percent. By comparison, Adblock Plus saw a 40.1 percent reduction. Perhaps more significantly, though, Tracking Protection reduced the median load time of the top 200 websites by 44 percent, and data usage by 39 percent.

Internet Explorer has had a similar feature since the release of IE9, called Tracking Protection Lists (TPLs). Like Firefox, TPLs are off by default. Chrome allows you to set the Do Not Track flag, but does not provide a blacklisting feature (it would be in conflict with Google's main revenue source: advertising).

The Do Not Track (DNT) initiative, which burst onto the scene in 2012 (with backing from Obama no less), has not been massively successful. DNT asked that web service providers honour the user's preference on tracking cookies. Unsurprisingly, given that so many websites are funded through targeted advertising, DNT never really took off.

Tracking Protection is the "nuclear option"—on the one hand, it certainly does a good job of blocking the user from being tracked, but it also neuters one of the major sources of revenue for almost every free website and service.

As Monica Chew sees it, Mozilla should be the "driving force" of "alternative revenue models" that better protect the privacy and security of Web surfers. She seems to be implying that Mozilla should turn on Tracking Protection by default, and then see how the Web adjusts. Given the backlash that Microsoft saw after enabling Do Not Track by default in IE10, it is unlikely that Mozilla would ever be that heavy-handed.

Websites, for their part, do seem to be aware that a business model based on ad revenue isn't sustainable. Alternative revenue sources, such as native advertising, sponsorships, events, and subscriptions can all make good money.