A really cool string I pulled off . <| sep |> You don ' t need WiFi . WiFi is just wireless fidelity the internet sent over a wireless connection . You can use the internet just fine with an ethernet cable , but then you ' re stuck with your device physically connected via cable , which makes mobility a little more difficult . WiFi takes that signal and turns it into radio waves that are broadcast to your device instead , communicating with radio waves in the air instead of the movement of electrons in a metal wire . As for why YouTube will continue playing after an outage your video does what is called buffering , which means you are not streaming your video constantly , with each frame coming from the YouTube server the moment you need it . Your computer requests the full video and begins playing the video before you finish downloading it , but you download it much faster than you ' re watching it . For simplicity , imagine you ' re watching a video playing at 30 frames per second , but you ' re downloading 60 frames per second . For each second of video you watch , you download an additional second of video to watch in the future , so by the time you ' re halfway through the video , the other half is already saved by your browser . If your internet connection fails , the video is already there in your browser waiting to be watched . It won ' t load anything else , of course , but as long as you ' re just watching that same video it doesn ' t matter . If the video is particularly long , you may download a good chunk of it and be able to watch for several minutes before you run out , but you will eventually run out , until your internet connection comes back and your browser starts buffering again . The internet does this on purpose , so it can share the workload of many computers using limited bandwidth . If every computer was streaming the video in real time all the time , the server would have to maintain every connection throughout the whole video . That ' s wasteful just maintaining the connection takes a little bit of extra bandwidth . Instead , it gives as much of the video as it can to one computer , then ignores it for a little bit and gives as much of the video as it can to another computer , and so on , making sure that for each computer it never ignores it long enough that you run out of loaded video and the video stops playing . Obviously , it ' s more complicated than that , because you ' re talking about thousands , if not millions of computers accessing the same data at the same time , but that ' s the easy version to understand , and that ' s why buffering exists . TLDR You don ' t need wifi , but you do need some kind of internet connection , and your video will not play without one . However your video might continue to play after your connection drops if it has already loaded the video into your browser .