Lots of image "optimizing" CDNs will return WEBP images even if the URL specifies JPG, as long as the browser indicates support in the Accept header. As far as

Lots of image "optimizing" CDNs will return WEBP images even if the URL specifies JPG, as long as the browser indicates support in the Accept header. As far as I know Chrome (nor Firefox) will "convert" images from one format to another when saving, so if Chrome is saving images as WEBP, it's because that's what the website is serving you, even if the URL say it's a JPG.