Mozilla proved its tracker blocker cut news page loads 44% and won a best-paper award

On May 21, 2015, researcher Monica Chew announced that her paper with Georgios Kontaxis had won the best-paper award at the Web 2.0 Security and Privacy workshop. Re-running the performance evaluation on top news sites with Firefox's Tracking Protection enabled, they measured page load time down 44% — even higher than their August 2014 Air Mozilla talk — because news sites are dense with embedded third-party content.

Chew added an emphatic correction to the post: several reports had described the paper as being about cookie blocking, but Tracking Protection blocks all traffic to tracking domains, not just cookies. That design choice is why the speed gain was so large: a cookie-only blocker would leave the requests, the bandwidth and the load cost in place.

She called the paper the last artifact of her Mozilla work, having left the company at the beginning of April 2015, and used it to argue that current advertising practices are in direct conflict with security, privacy, stability and performance. Advertising, she wrote, does not make content free; it externalizes the costs, which is what incentivizes outcomes like ad-injection malware on roughly one in twenty machines and sites that need unsafe plugins and twice the resources to load.

The announcement drew 491 points and 288 comments on Hacker News on May 23, 2015. The debate turned on whether blocking trackers helps users or starves the ad-funded web; commenters noted that Mozilla itself ran Google Analytics, and a Mozilla employee replied that enabling the experimental Tracking Protection blocks Google Analytics on Mozilla's own site.

Block all requests to known trackers, not just cookies, then publish the page-load saving as peer-reviewed proof

It measured real sites rather than a lab: rerunning the evaluation on top news pages showed 44% faster loads, higher than the earlier talk, because news pages are dense with third-party requests

The feature blocked entire requests to tracking domains rather than cookies, which is what made the speed gain visible and the privacy protection real

A peer-reviewed best-paper award gave the figure institutional credibility, so it could not be dismissed as Mozilla marketing

It reframed a product under attack as user-side value: instead of asking publishers to surrender ad money, it showed in seconds what trackers cost readers

A measured, externalized cost converts a values fight into an engineering tradeoff: block whole requests to trackers, not cookies, and let the number argue for the feature.

The post was the last artifact of Chew's Mozilla work: she had left in early April 2015 and used the award to argue that Firefox must act as a user-agent rather than an industry-agent. The Hacker News launch drew 491 points and 288 comments on May 23, 2015, with the discussion centering on whether blocking trackers helps users or undermines the ad-funded web. The blog reports no default-on ship date; what it left behind was a citable, measured figure that reframed tracker blocking as performance engineering.