Historically interop seems to have been focused more on CSS, but that's changed more and more. Even still many of the test areas include tests for workers, ensuring that the state of PWAs will also improve. And in 2023 they had an entire Modules section which heavily tested PWA/worker-specific functionality. Additionally, many of the APIs tested and investigated like OffscreenCanvas and mobile testing are very relevant to many PWA applications.
This year, like the year before, is the least CSS-centric interop. With sections for IndexedDB (which I've only ever seen relied on by PWAs) and Websockets and important accessibility improvements. And the 3 investigation areas (WebAssembly, Accessibility, and Mobile testing) are all very relevant to PWAs.
What (other?) specific APIs are you interested in them focusing on?
Both of those websites include APIs that were implemented unilaterally by Google, while both Mozilla and Apple rejected them – mostly on privacy and security grounds. They aren’t a part of the web platform and aren’t on any standards track, they are Google APIs.
The web platform is not defined as “whatever Google chooses to implement”. It’s a collaborative effort.
All of those browsers use Blink, Google’s rendering engine. It’s one single implementation. Something needs two independent implementations to become a web standard. If you look at the specifications, they will explicitly state that they aren’t standards.
An interoperability project isn’t going to consider working on things that have been explicitly rejected by every implementer but one. That’s not how interoperability happens.
Google need to go back to their specifications and resolve all the security and privacy problems with them so that they can convince at least one other rendering engine to implement them. If they can't do that, there’s no chance they are candidates for interoperability work.
From what I remember, the consortium is maybe a dozen people? And these people also work for the browsers. The goal is to come together and find features that they all can work on or improve over a year, taking into account current roadmaps and workloads. Think of interop like the small extra tickets you can work on in between the main feature development at your day job.
Right now the focus has been very low level details about how browsers render content. These are the biggest areas for improvement as the JavaScript APIs are largely standardized and merged in from “upstream”.
I suspect we will continue to see more work done to patch holes between browsers, before we see a push to simultaneously implement new features across all engines at once.
That said, with Apple finally adding webpush to mobile Safari, we’re getting a lot closer to covering the needs of the vast majority of web apps that would benefit from PWA features. What sort of features are you wanting to take advantage of that are not present cross browser yet?
You link to https://web.dev/learn/pwa/capabilities and https://whatpwacando.today elsewhere, but I think many would consider many of those features to not be inherently PWA features. Many, _many_, of those features have wide usage outside of PWAs, which makes putting them into a "PWA" bucket somewhat meaningless. Constructing buckets like "Storage" or "Media" would probably be more meaningful to web developers.
If you look at the basic definition of PWAs, it's primarily about manifests and service workers, and about using the web platform in combination with these.
Manifests are hard to test automatically — their content is largely shown in differing parts of browser UI, and UI is by-and-large unspecified in web standards (because vendors want freedom to make their own UI decisions) — which makes including them difficult. It's also unclear how much there is in way of interoperability problems.
Service workers are definitely something that could be proposed (though haven't been in recent years); I again don't believe there's been that much in way of interoperability problems there recently.
One of the focus areas for this year is IndexedDB. And many of the other areas contain tests for service workers. I don't think it's accurate to say anyone's dragging their feet. Apple's done a 180 on PWAs in the past year. I also don't know what you mean about Firefox dropping pwa support. They've been hard at work improving the PWA scene for years now. And they're docs are the go-to for anyone working on one
In what way has Firefox dropped PWA support? They continue to support all the major APIs relevant to PWAs. Which you can see a thorough list of on Mozilla's MDN docs here:
Why do we think there isn't a PWA focus area from the participating consortium?