I have the suspicion that you all get the question wrong.

If I understand @smolcatgirl correctly, she wants true video streaming.

What send_file or Plug.Static do is to send the whole video file to the browser.

So she wants partial video streaming. Like buffering x amount of seconds ahead of current playtime or if the user starts the video from the middle, don’t even load the first half.

I can’t give an answer for how to do this but I hope someone else might have an idea.

Well this article is outdated but have very useful information: https://medium.com/@miguel.coba/streaming-video-with-phoenix-31cd6c3048e . Not hard to make it work with the lastest version of Phoenix.

But the problem when you want to stream videos is to allow different qualities/bitrate depending on bandwidth and/or device screen-size/performance.

It depends on the player.

I often use jwplayer which has an option for playlist. With a playlist in automode, then I can run multiple videos.

But it is a commercial product.

You might hook an event when the player stop to play.