Open a browser's network tab and you'll see Cache-Control and ETag sitting on the response headers of nearly every image, stylesheet, and script. Most developers recognize both names, but far fewer could explain how they actually divide the work of caching between them. This post walks through the basics of HTTP caching, then looks at how this project's own OGP image generator uses one of these headers and deliberately skips the other. The Problem These Headers Solve Note: ...