All output images will be zipped after the uploading and processing job finished.
Image optimizer online helps to auto calculating the best smallest image size belong with highest quality. Additionally, the smaller image size will decrease the page load time and improve Google Pagespeed Insights score of your website.
Since Google has turned down the PageSpeed Service, there is no way to download the optimized images from Google Pagespeed Insights page. This tool followed strictly this documentation to optimize your image that can be passed image validation on PageSpeed Insight. For other purposes, you can use this tool as png optimizer and jpg optimizer.