Ask HN: How does WebKit ITP work?

I recently heard about a feature of WebKit, ITP(Intelligent Tracking Prevention)[0] and I'm curious as to how it works. Specifically, I'm curious whether other browsers that use WebKit on iOS are making use of this functionality by default, since articles about ITP make imply that the default setting is "enabled".

Is this technology transparent to the developer building on top of WebKit, or are there specific APIs that have to be invoked in order to use this technology?

[0]: https://webkit.org/blog/7675/intelligent-tracking-prevention/