The Rules of Adblocking: How Block Lists Work

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.

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