Monetisation & Revenue
Ad Blocker
Also called: adblock, ad blocking
An ad blocker strips the ad slot before the page renders, so no impression is recorded and nothing is paid. Those views still land in your view count and in the denominator of RPM, which pulls the figure down with nothing wrong at your end.
Blocking is far easier in a desktop browser than inside the mobile and TV apps, so the size of the effect follows where your audience watches. YouTube's answers to it are detection prompts and Premium, whose subscription fee is shared out to the creators a subscriber actually watches.