They say a picture is worth a thousand words. But online, a picture can be worth a thousand kilobytes or more! HTTP Archive shows that images make up 64% of a web page’s total size on average. Given this, image optimization is key, especially considering that many users will abandon a request if it doesn’t load within a few seconds.
The problem with image optimization is that we want to keep file sizes small without sacrificing quality. Past attempts to create file types that optimize images better than the standard JPEG, PNG and GIF formats have been unsuccessful.
Source: Smashing Magazine