Compressing images before uploading them online saves both bandwidth and online storage. Kaken claims to achieve good lossless and lossy compression without compromising the quality of images visibly. You can upload your files from your desktop, use Kraken to compress them and finally download them individually or all in a zip archive. When I tried some of my images including a 3.6KB image I wasn’t disappointed. And I must mention that Kraken is fast.