With whom is Apple competing on their own web pages and apps? And how much advantage does some shiny reflection (which, btw, could also be attained by writing the effect yourself) offer them over that competition? It must be something big and obvious, otherwise there's no way it's illegal, but I can't think of it.

If you mean "anti-competitive" without referring to monopolies, then, well, every company does that.

Google or any open source map product. And actually, if we use the SCOTUS approved DOJ v MSFT consent decree as precedent, any app that can't use this private API component would be an impacted party.

I'm an antitrust nerd - 20+ years since I made my first PACER account as a teenager to get documents from interesting cases..

95% of what people call "anticompetitive" or "monopolistic" has no legal bearing. People don't know the legal definition of those words and bandy them about based on vibes.

This however, is a very very clear case of violations of precedent. If we look at Microsoft's final judgement https://www.justice.gov/atr/case-document/final-judgment-133 see F(1)(a), H(2)(b), while these stipulations haven't been applied to Apple, if I were in a market dominant position, I'd be super careful about capricious restrictions like the example undocumented API, and behavior that mimics patterns of activity that were seen as actionably sanctionable to similar market dominant forces

It’s a way they can make their webview-based apps look “native” more easily than a third party can. If you try out a third-party app and it looks less well integrated visually than a similar first-party app, then the latter has a competitive advantage because of that.

Well for starters, no one else is allowed to publish a browser with their own engine on the AppStore, and they've hampered sideloading for years. In a vacuum, it might be reasonable to block any third-party browser engines, or to put something special in their own that no one else can use on the phone, but combining those is just intentional sabotage. And yes, I know that this specific CSS property isn't all that important, but having an argument about how much they're allowed to intentionally sabotage other browsers on their phones is at best a misguided distraction from the point that they shouldn't be doing it in the first place (and not a particularly good defense either; try arguing with a cop who pulls you over for speeding that the law you broke wasn't really that important and see if it gets you out of the ticket).

> With whom is Apple competing on their own web pages and apps?

With every other app using a web view.

> without referring to monopolies

Of course it’s about monopolies. Safari is still “privileged” to be forced default browser. Making an alternative, Apple ensured to be very hard and expensive. So gating any kind of first party feature is a big no.