This document currently caters to enthusiasts who don't mind getting their hands dirty with the internals of HTTP, networking and the browser.
Technically, TwoSeven can enable sync of arbitrary HTML-5 videos found on the web. Once the URL of such a video is obtained,
paste it in the search-box with a prefix of url:.
Try pasting the following in the search-box:
url:https://www.quirksmode.org/html5/videos/big_buck_bunny.mp4
Similar to the above arbitrary videos, TwoSeven can also enable sync of HLS videos from the web.
The HLS player requires a link to an m3u8 file. The path to these files can be obtained easily via the developer console on your browsers.
Once the path has been obtained, paste it in the search-box with a prefix of hls:.
You can test this feature with this freely available HLS video:
hls:https://content.jwplatform.com/manifests/vM7nH0Kl.m3u8
Keep in mind that a large fraction of media content on the web is protected by server-side checks that search for the existence of some sort of cookie/token on the client's browser. Often, these tokens are used to ensure that a user has navigated through certain pages (and associated ads). Many websites also attempt to verify that the token matches the IP address of the client to which the token was granted. These checks mean that your friend may not be able to directly use the URL shared by you. In such cases, it may be sufficient for your friend to visit the page containing the video and then use the URL.