| Most larger ad networks track post-view conversion - that is, someone viewed an ad but didn't click on it, and then later visited the advertiser's site anyway - using a "conversion pixel." The ad network provides each advertiser with a HTML or JS snippet that loads an 1x1 pixel image or makes a similar small HTTP request to the ad network. The ad network records a post-view conversion if either: 1. The ad network cookie that was set when the ad was served is still present, or 2. A user was logged in to the publisher's site (Google, Twitter, etc) when they viewed the ad, and is also logged in when they visit the advertiser's site. #2 is also how most cross-device tracking occurs. For example, if you're logged in to Twitter on your phone and see a Twitter ad, then type in the advertiser's URL on your desktop where you're also logged in to Twitter (and the advertiser has Twitter's conversion pixel on their site), Twitter will record a cross-device post-view conversion. Here are examples: Twitter: https://business.twitter.com/en/advertising/campaign-types/i... AdWords (for YouTube impressions): https://support.google.com/adwords/answer/2375431?hl=en Facebook: https://www.facebook.com/business/a/performance-marketing-st... Aside from blocking the ads, uBlock Origin blocks the conversion pixels/requests for the largest ad networks. Often a conversion pixel snippet is used alongside retargeting/remarketing. Some ad networks use #2 above to do quite sophisticated retargeting, not just targeting those who viewed a specific page. For example, Google lets advertisers retarget AdWords ads to those who liked a video in the advertiser's YouTube channel: https://support.google.com/adwords/answer/2545661?hl=en&ref_... |