A deep, deep, deep dive into the JPEG format. Best of all, it’s got interactive explanations you can tinker with, a la Nicky Case or Bret Victor.
You’ve probably seen this already, but it’s really worth bearing in mind: when you’re scaling up JPGs for retina display you can safely reduce the image quality by quite a lot—to the point of getting the exact same file size as a higher quality image that’s half the size.
Handy web-based tools—compress HTML, CSS, and JavaScript, and convert files from one format to another.
Following on from Amber’s introduction, here’s a really in-depth look at image formats, compression and optimisation techniques from Addy.
This is a really nicely put together little web book released under a Creative Commons licence.
The interactive widgets embedded in this article are excellent teaching tools!
This is a superb explanation of flexbox—the interactive widgets sprinkled throughout are such a great aid to learning!
Sprinkle some machine learning on image optimisation.