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ImageEngine is a free Wordpress plugin which works seamlessly with Woocommerce product images. Google suggests the use of an Image CDN to serve images on the fly. Images account for the majority of requests and bytes downloaded by the browser. ImageEngine has a free plugin for Woocommercy. The most important settings to pay attention to is the CDN hostname and the checkbox is ticked if your site is on https (which it probably is) An ImageEngine CDN is included in Jetpack.