As mentioned in the previous chapter, mobile networks have many limitations compared to a wired connection. So, reducing the file size as much as possible is really essential in mobile web development. According to the data (https://developer.yahoo.com/performance/rules.html), 70-80 percent of sites' bandwidth is consumed by the images. Therefore, delivering smaller file size images with acceptable quality to the mobile will always provide a better outcome.
When it comes to image optimization, there are two key factors that you need to always keep in mind. They are as follows:
Resize your images to correct image resolution
Reduce the file size.