Use of Tracking Cookies on the Rise as Advertisers Seek More Data From Web Surfers

Use of Tracking Technologies Up 23% From Last Year

By Published on .

The number of cookies dropped by websites is growing.

The number of third-party cookies -- little pieces of software set on users' machines to track web users for ad targeting or site analytics purposes -- rose from 1,887 on the home pages of the most-popular 100 websites in May to 2,324 in October, according to research from the University of California at Berkeley Center for Law and Technology. That's a 23% leap.

The Center's Web Privacy Census, conduced each year, crawled the most-trafficked sites on October 24, measuring the number of first-party and third-party cookies spotted on the top 100, top 1,000 and top 25,000 sites. In addition to checking website home pages, which it calls a "shallow crawl," the census project conducted "deep crawls," checking up to six random links on the same sites.

The privacy census measured the top sites as reported by Quantcast. According to the Quantcast site, the top 10 U.S. sites are Google, YouTube, Facebook, MSN, Twitter, Yahoo, Amazon, Wikipedia, and Huffington Post. Others in the top 100 include, eBay,,, IMDB, WebMD, Politico, Flickr, BuzzFeed, and Time .com.

Data management platform and exchange Bluekai set the most cookies on the top 100 sites in October -- 328 up from 321 in May, according to the U.C. Berkeley study. The census reported that Bluekai also set the most cookies among the most popular 1,000 sites. However, in that category the number of cookies it dropped fell from 2,906 on May 17 to 2,562 on October 24.

Bluekai CEO Omar Tawakol argued that the majority of the company's data capture is conducted for first-party use by site publishers. "The Bluekai first-party [software-as-a-service] business and data capture exceeded the third-party exchange business" in terms of revenue and raw data starting in the middle of this year, said Mr. Tawakol.

Companies such as Bluekai "tend to frame privacy issues as ones involving use, rather than collection of data," noted Chris Hoofnagle, director of Information Privacy Programs at the U.C. Berkeley Center for Law and Technology, in an email. "We are focused upon collection, because it is impossible to tell what uses are being employed by companies and because these companies change their policies, sometimes secretly," he added.

"We saw statistically significant increases in tracking vectors in all three groups," said Mr. Hoofnagle, referring to the top 100, top 1,000 and top 25,000 site lists. However, he added that the top 100 and 1,000 lists are "the most important [because] most individuals' browsing is concentrated on very popular sites."

It's not only advertisers that are mining for data gold. Publishers also are increasingly recognizing the value of their audience data. Site publishers - from newspaper sites to ecommerce sites - are piling on more and more tracking technologies to better understand their audiences and sometimes to sell their audience data to data aggregators and exchanges.

Among the top 1,000 sites measured in May and October, nearly 98% set cookies, and around 85% had cookies set by a third party.

Most Popular