How Swift Performance handle data which was sent to the API?

Swift Performance will send the HTML source, CSS and Javascript to the API. If you don’t enable caching for logged in users (or you do, but you also enable Shared Logged in Cache), then only public ​data will be send to the API. In that case personalized data wouldn’t be send at all. The optimized files may will be kept for a short time in cache to be able to serve repeated requests.
Image Optimizer it will send the image to the API, our API server optimize it and send the optimized version back. After this, the API will drop all temporary files, none of images will be kept on our servers, they will be deleted once optimization finished.
We won’t use any third party services, so data what you send to the API won’t be shared with others. API is using SSL, Image Optimizer is using raw connection. Because this it is recommended to optimize only public images with Image Optimizer.