I think the most common and critical failure mode I’ve seen is when websites wrap click handlers for important conversion events (ie “Complete Purchase” or “Joi

I think the most common and critical failure mode I’ve seen is when websites wrap click handlers for important conversion events (ie “Complete Purchase” or “Join Mailing List” buttons) in a call to a tracking script. Google Tag Manager has a callback system that makes it really easy to trigger an event and wait for all the tracking pixels to fire before you advance someone to the next page, “guaranteeing” that you capture the events. If GTM is blocked and no effort has been made to handle a case where it didn’t load, however, the Complete Purchase button just straight up won’t work. I debugged this behavior in a high traffic site several years ago and have since noticed it all over the internet. With how widespread ad blockers are these days–especially in some demographics–I’d consider it an important QA step to ensure that customers can actually pay you even if they’re blocking ads and trackers.