Lightbox ads are a type of expandable ad that can expand to a very large size (up to 1000x600 pixels). When a user chooses to engage with a Lightbox ad (by hovering the cursor over the ad for two seconds) the ad then expands to the center of your page. Once the ad is expanded, a translucent layer grays out the background of your page, giving the user a near full-screen ad experience. Lightbox ads are a high-engagement format and are only available on the Google Display Network (GDN).
Lightbox ads are served as third-party ads and are created by Google-certified rich media vendors for the top display advertisers in our network. Advertisers pay for Lightbox ads on a cost-per-engagement (CPE) basis which means that you generate earnings from Lightbox ads when a user chooses to engage with the ad on your page, i.e., by hovering over it for two seconds to expand the ad.