Responsive Images
We should always aim to build websites and applications to be as lean as possible. The benefits of faster sites are well documented for all meaningful metrics. As far back as 2009, Google was publishing its findings on the importance of page speed: https://services.google.com/fh/files/blogs/google_delayexp.pdf.
Images are by far the biggest contributor to website “weight,” a significant contributor to web page speed, or lack thereof. Looking at the data from the 2021 Web Almanac at https://almanac.httparchive.org/en/2021/page-weight#images, we can see images accounting for almost twice as much weight as the next largest resource, JavaScript:
Figure 9.1: A bar chart showing that images are far and away the largest resource
Furthermore, research carried out by Google in 2017 suggested that “the probability of bounce increases 32% as page load time goes from 1 second to 3 seconds” and that “…53% of visits are...