danburzo

Keep in mind this shows the “live most polluted major city ranking, 11:00–12:00” (EEST time), so rather short-term measurements.

Thanks! I’ve updated the introduction with some ‘now vs then’ pointers.

Updated the article with some information on the `Vary` and `No-Vary-Search` headers. I’ve left out the details of how revalidation works with `Vary` since I haven’t been able to reconcile yet what the spec seems to encourage vs what the tests on cache-tests.fyi suggest is conformant behavior.

As many have pointed out here, the nature of caching has changed in the current climate of ubiquitous HTTPS, and I want to add a paragraph or two about it. Is there a good summary somewhere that I could reference? What are the the usual, most prevalent uses of HTTP intermediaries involving caches, besides CDNs and origin-controlled caches (eg Varnish)?

I’m sorry you didn’t get anything out of it. I wasn’t operating at the edge of caching knowledge, just a person refreshing and clarifying for themselves how caching works. Some things were new to me, and after spending so much time with the RFC, I just thought others may benefit or, more selfishly, would point out errors or ways to make it better.

I mean, do those <meta> tags really suggest someone who’s into SEO? Call me stale but what I really want is validation :-)

This is exactly my jam!

May I suggest adding a distinct style for visited links, so it’s easier to keep track?

With the goal of showing nice, clear images to as many devices as possible, while optimizing the file size, I would:

1. decide if I want to use any of the newer image formats. If so, each needs its own `<source type=''>` in a `<picture>` element, front-loading the most efficient formats. 2. decide if I want to serve different densities for the image.

For specifying densities, width descriptors + `sizes` attribute will always compute to a more useful effective density than density descriptors, if you can get `sizes` in the ballpark of how the image is actually laid out.

For lazily-loaded images, `sizes=auto` will do that for you, when it becomes universally supported.

Thank you for the kind words! I have fun reading specs, but the HTML Standard is denser and organized more… cross-referentially than the average CSS spec, so there was a bit of putting-things-together.

Thank you for the kind words!

I haven’t explicitly mentioned it in the article, but `srcset` + `sizes` is a way to provide dynamic densities for one image format, then multiply that with one `<source>` for each image format:

    <picture>
      <source srcset='…' sizes='…' type='image/avif'>
      <source srcset='…' sizes='…' type='image/webp'>
      <img srcset='…' sizes='…'>
    </picture>

If this is what you mean, maybe it would be better to include in the article?