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YouTube takes on the cable TV providers
Vimeo is a social media app that lets you share and capture videos. You can watch new videos in a variety of different categories, and you can share your own content right from your device. Read more about Vimeo.
Federated (ActivityPub) video streaming platform using P2P (BitTorrent) directly in the web browser...
As /u/Fett2 said, imagine you have a website that hosts dog videos and another that hosts cat videos. If you want, you can be on the dogs website and still view cats videos without leaving the page. (They have this same example on their page https://joinpeertube.org/ ).