In this presentation we’ll review the current state of web privacy and discuss experimental browser features aimed at improving privacy protections on the web. We’ll review one mechanism in particular - "origin attributes" - which provides an extension to the web’s regular same-origin policy. Firefox has used this technology to implement the Tor browser's concept of 'First Party Isolation' natively rather than the need for a separate build. This technology also allows us to experiment with user-centric privacy features, such as with the Containers feature, which allows users create isolated browsing containers to keep their online identities separate. This presentation is also call for anyone concerned with privacy to perform their own experiments and contributions. The technology behind Containers is now exposed to Extensions, so that you can build your own features on top of this technology. We’ll go through the details of this technology, the benefits and limitations of the mechanism, and run through a sample extension to get you started experimenting.