Third-Party Cookie Blocking Grows

NEW YORK More consumers are rejecting third-party cookies, according to a new study, making it more difficult for Web analytics providers and ad networks to track Web users.

WebTrends, a Portland, Ore.-based Web analytics provider, found blocking of third-party cookies – the tracking files used by entities other than the site a user is visiting – increased from 2.4 percent in January 2004 to 12.4 percent in April 2005. WebTrends attributed the rise to the adoption of Firefox and updated Internet Explorer service pack that reject third-party cookies as a default.

“We’re starting to see a trend,” said Jeff Seacrist, director of product marketing at WebTrends. “We may see these numbers continue to increase.”

The study examined data from WebTrends customers over a 15-month period, including more than 5 billion visitor sessions.

The WebTrends report follows survey data that showed over 40 percent of Internet users say they delete their cookies regularly. A report by aQuantive’s Atlas Solutions unit found third-party cookies bearing the brunt of deletion: 32 percent of consumers deleted them weekly and 48 percent monthly. While deleted cookies skew tracking, they can always be reset, unlike cookies blocked outright.

“This rejection issue is more serious than cookie deletion,” Seacrist said.

WebTrends is addressing the issue by trying to avoid using third-party cookies altogether. Since users are less likely to block cookies from sites they visit, WebTrends is moving its clients to use first-party cookies. While a majority of its clients use third-party cookies today, Seacrist expects most will move to first-party cookies in a year’s time.