The amount of research and testing that had to go into this demonstrates how fractured and broken web performance is right now.
But, since it is, there's a useful snippet at the end of this article.
Google Fonts is fast. Now it’s faster. Much faster.
Stephanie Stimac: Location, Privilege and Performant Websites
Unconscious privilege hides in delivering so much unused code to customers. In not taking the time to understand what the implications are of using the code you choose to use and how large those files are, we assume that all of our customers are in the same situation with the same access to resources.
NPR smartly chose to build a text-only website so that people with limited internet connectivity during Hurricane Irma could receive up-to-date news.
If you do assess your code and for whatever reasons find that you cannot reduce the size of your website, be it time or staffing propose adding a text-only website, especially if you provide a service that is essential to most of the population in your area.
Assuming all of your customers are living the same life, with the same privilege, with the same access to fast internet and data is the quickest way to ensure you’re excluding some of them and not providing the same level of service the rest get. It’s most likely not even happening intentionally, bias is inherent in us all in some way or another. Bias based on location is something I hadn’t considered before my experience on a subpar network due to where I live.
Testing on a
Ann Robson: Progressive jpegs: a new best practice (Performance Calendar)
And even though not all current browsers make use of progressive jpeg’s progressive rendering, the ones that do really benefit, and we get file size savings across the board. It’s our best option today and we should use it. Progressive jpegs are the future, not the past.