Google yesterday unveiled its lightbox display ad format, which it calls the first of a new family of display ads that "allow marketers to pay only when a user engages." The lightbox starts as a standard display ad (which makes it scalable), but after a two-second hover, expands to a "super-sized canvas."

Google claims that in internal tests, this smart hover feature eliminates nearly 100% of accidental expansions, and increases engagement by 6-8 times over standard click-to-expand ads. So, users engage only with ads they really want to see, and brand marketers only pay for truly engaged views

As Marketing Land describes, the expanded ad appears in the middle of the screen and dims the page behind it (see graphic, from the Anthropologie online catalog).

This pay-only-for-engagement model is similar to Google’s True View video ad formats on YouTube and on the Google Display Network (GDN). Google analyzed the sales impact during and after 92 ad campaigns, and claims that on average every $1 invested in YouTube delivered a $1.70 return in sales, or 2.4 times greater efficiency than for the TV spend for those same campaigns. Google claims that on average, ads on YouTube and the GDN drive a 36% increase in visits to websites and a 36% increase in searches for brands online.