Facebook says its Live videos are wildly popular and generate around six times the interaction other videos do. That's why it's testing a new feature that adds the elements responsible for making Live a more engaging, interactive experience to non-Live videos on the platform. Starting today, select Groups will have access to "Watch Party," an experimental tool that creates a shared experience for multiple users. It allows administrators to post any public video on their Group, which members can then watch together at the same time. (Also, it probably helps that a billion accounts use Facebook Groups every month.) They can even leave comments and reactions that show up on screen the same way they do on Live, whatever it is they're watching.