At WWDC 2017 in San Jose, CA, Apple took the wraps off the newest version of their web browser, catching up to the competition in some areas and further encouraging their role as the private-by-default mobile phone vendor.
Safari 11 will now suport WebRTC, the in-browser, real-time communication standard. This brings Safari up to parity with the remainder of current generation web browsers. We knew this was coming since Apple checked-in the first batch of WebRTC code back in January. The arrival of WebRTC means that iOS devices will now have two built-in video chat applications, adding to the built-in FaceTime app. Apple has said that WebRTC was the "#1 most requested web platform feature for Safari". In a blog post, they mentioned that they currently support legacy WebRTC APIs, but that they will be "disabled by default on future releases". For now, they support the HEVC and H.264 for video.
Apple will also ship WebAssembly in Safari 11. Both WebRTC and WebAssembly are now available in Safari Technical Preview 32.
A new, privacy-focused feature dubbed Intelligent Tracking Prevention lets Safari reduce "cross-site tracking by further limiting cookies and other website data".
Intelligent Tracking Prevention collects statistics on resource loads as well as user interactions such as taps, clicks, and text entries. The statistics are put into buckets per top privately-controlled domain or TLD+1.
Using on-device machine learning, Safari takes the collected statistics and determines which third-party domains to restrict. This work is a part of a growing set of tools to restrict tracking online. The Brave web browser already blocks ads and trackers while Firefox has a Tracking Protection when using private window browsing. In addition, the EFF has a tool called Privacy Badger that stops third-parties from tracking users as they move about the web. This is a different tack than typical ad blocking. Often these trackers have no visible elements to distract the user, so they are described as silently tracking user behavior.
On Hacker News, an Apple engineer said this feature does as much as it can without impacting the user's experience:
We're trying to do the most extreme thing we can do short of blocking ads. To be more effective, you end up blocking ads, whether intentionally or as a side effect. This blocks more than just cookies by the way, it affects all client-side state. And client-side state is still the primary and most reliable tool used for tracking, even though other methods exist, such as browser fingerprinting, behavioral fingerprinting, and IP-based tracking.
The advances in Safari 11 are all positives for the web and its advancement, but some developers were chagrined to learn that there was still no support for Service Workers.