The new content-visibility CSS property explained by Surma and Jake.
Topic: Performance
A look-back at caching strategies from the past; with recent changes in Chrome's and Safari's caching strategies, there is no caching benefit from using publicly available third-party libraries anymore.
Improve the loading of your responsive images by using link rel="preload" elements with the new attributes imagesrcset and imagesizes.
Learn how your visitors navigate your sites by using the Navigation Timing API in JavaScript.
Article on headers that can be used to provide a better user experience making the web safer, affordable and respectful.