Declarative partial updating "sets the stage for client-side includes." https://github.com/WICG/declarative-partial-updates

The linked article suggests a potential syntax:

  <template for="footer" patchsrc="/partials/footer.html">

That would transclude the content of /partials/footer.html in your HTML.

But the road ahead for this is still quite bumpy. Here's a good video from a year ago, talking through the obstacles. https://www.youtube.com/watch?v=t0NBcve0enY

Very odd proposal. The new element syntax is perhaps the boldest choice. I wonder why they thought that was necessary. The idea of using this to defer rendering elements is also odd. So this would use a http long polling style? It really goes against several decades of progress in the web platform, where by now it's long established that you do this sort of thing with xhr. I'm amazed that they even put this in chrome, let along are saying things like "let sites use this new functionality right away even before this lands in other browsers" as if it's a sure thing.

  <p>
    <em>Some <?start name="hl"?>text</em>
    to replace<?end name="hl"?>.
  </p>

Wtf?

I can't really tell how you'd even use this. Is it supposed to be some sort of micro-optimisation thing to do with how HTML is parsed (now you can download chunks out of order, presumably with some performance gains since it's browser native?).

When I saw the title I was hoping it was going to be a very simple React-like API for constantly updating parts of the DOM with maximum performance since the browser devs are now involved. It doesn't look like that's what this is at all. And all these years later I'm still wondering why browsers aren't implementing an API like that when it's been obvious for over a decade now that real-time DOM updates are a vital browser feature that needs to be performant, and that developers vastly prefer a declarative model to a procedural one. Why after 15-16 years are we still building 100 versions of the same abstraction in user-land to turn Element.append into "refresh these elements when this data changes"?

I scanned the page but didn't get -- why? What problem does it solve? Why is a browser in the business of taking care of content update? How is this better than existing solutions?

Is this a Google-only proposal? Has Mozilla provided their thoughts on the matter?

So htmx?