This note is a layman’s guide to how the “block lists” that power adblocking work. A block list contains tens of thousands of rules that govern how a website should be displayed. There are two types of rules. “Filter” rules define what should be blocked. “Exception” rules define what content should be displayed. The most popular block list, “EasyList”, contains tens of thousands of these filters and exceptions.
Facebook’s decision earlier this year to start serving ads to adblockers is already starting to bear fruit. In last week’s Q3 earnings call, the company said that “desktop ad revenue grew 18%, which is higher than growth rates in recent quarters, and was aided by our efforts to limit the impact of ad blockers on advertising served via web browsers”. This post examines these figures to extrapolate the revenue lift that Facebook will enjoy from serving ads on the blocked web. We estimate that Facebook's decision to show tamper-proof ads will yield an additional $720 million over the next year.