WebP images in banners

Anyone used WebP images in their banner ads? In a recent ad campaign, the image-dense creative tipped us over max file size requirements. My solution was to use WebP instead of PNG for silhouetted photographic images, which worked great.

I informed the client of the small % of browsers (IE) that wouldn’t display the images. The ads were given the green light and proceeded until they hit the ad server’s test preview. The preview didn’t render the WebP images in the ads.

My take is that the ad server’s test environment uses an Internet Explorer engine to generate its previews. The client was worried that the WebPs were being stripped out by the ad server. It was impossible to get an answer from the the ad server peeps, so rather than using WebPs, we used degraded-quality PNGs.

Thoughts on WebP use in banners?

I think we had this talk. Link here.

Yes, that thread is about using WebP in Hype, but not specifically within display ads. The subject gets mentioned there briefly, but I'm looking for confirmation from people who have successfully used WebP images within display ads.