What are some alternatives?
Shrink Me - Compress images with one drag / click
Cloudinary - Cloudinary is a cloud-based service for hosting videos and images designed specifically with the needs of web and mobile developers in mind.
Landscape by Sprout Social - An interactive tool for social media image resizing
Optimage - Advanced image optimization tool
TinyJPG - Compress JPEG images with perfect quality and file size
imgix - Real-time Image Processing. Resize, crop, and process images on the fly, simply by changing their URLs.