You want to use the Range header.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Ra...
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Ra...
Also interesting to note that it's not just HTTP it supports but other protocols I haven't heard of like DASH, HDP, HLS [1].
[0] https://github.com/subhra74/xdm/blob/master/app/src/main/jav...
[1] https://github.com/subhra74/xdm/tree/master/app/src/main/jav...