LoyaltyHarbour Image Optimizer

Can't recommend this app enough. I had mistakenly uploaded all my site images in a large file size and in the wrong format. My images were reduced to a manageable size in a number of hours (there were nearly 15,000 of them), which massively sped up my site's loading time. Further, they offered to change the format of all my images free of charge. They have gone above and beyond to help me - so friendly, so efficient.