Having to select an image compressor based on format seems like a redundant step.. Can the service not just automatically recognise the file format? Can you ex

Having to select an image compressor based on format seems like a redundant step.. Can the service not just automatically recognise the file format? Can you explain more about how the image gets compressed on the client side? Edit: I just tried it with a small png image (49kb), the site told me that it had compressed it down to 28.75kb. I downloaded the compressed version and it is 49kb..