Each site uses a large number of images. However, in 99% of cases, site administrators download non-optimized images. By not optimizing, we mean, by how much you can reduce the size of the image file without any reduction on quality.
["These PNG pictures have the same resolution, but weigh 50kb and 15kb respectively"]
You can achieve this image optimization with the help of the following programs: https://pngquant.org/, https://github.com/svg/svgo, http://www.lcdf.org/gifsicle/, http://jpegclub.org/jpegtran/ or the site http://imagecompressor.com/ We check the ability to compress images without losing their quality, but also recommend setting the compression of your jpg images to 80%. This saves up to 70% of the page load time.
["These two jpeg images have a different compression ratio; 95% and 80% respectively. In this case, they weigh 50kb and 15kb, respectively. "]