Google this week added WebP image format to Merchant Center. Advertisers can now submit a WebP (.webp) image as a valid value for the image_link and additional_image_link attributes.
According to Google, WebP (.webp) is approved besides JPEG (.jpg/.jpeg), PNG (.png), GIF (.gif), BMP (.bmp) and TIFF (.tif/.tiff) images.
Google says WebP is a modern image format that provides superior lossless and lossy compression for images on the web.