Blocking a URL or a CSS class name can be done very efficiently/easily with a browser extension, while running OCR on an ad (most ads are images/videos rather t

Blocking a URL or a CSS class name can be done very efficiently/easily with a browser extension, while running OCR on an ad (most ads are images/videos rather than pure text) to find keywords is much more difficult and computationally expensive. Apparently Princeton made it work, but it's definitely a much more difficult approach to take.