system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do ad blockers work?
gpt
Ads mostly come from known sources, known websites. They aren't generally served by the same site as you're visiting. So ad-blockers know a lot of these servers, and will block traffic from those servers.

They also know a lot of the HTML and JavaScript ads typically use, and will remove them from incoming HTTP responses before they get rendered.