[wallunit]

I'm very curious about Content Blocking Safari Extensions as well.

The old mechanism, that is the non-standard "beforeload" DOM event + synchronous messaging via canLoad, had it's issues. But the new one is entirely different from the hooks Chrome and Firefox provide to intercept requests. So I'm certainly not a fan of it either, as this makes it even more elaborate to port extensions relying on content blocking to Safari, and massively reduces the amount of code that can be shared between the respective Chrome, Firefox and Safari extension.

But even more importantly, I fear that it will have some shortcomings when it comes to blocking requests depending on its context (e.g. frame hierarchy). At least I'd be very surprised if they do a better job than Google did with Chrome's declarativeWebRequest API.

If somebody knows any more details about that new API please let me know.