when i download a mp4 file in getApplicationDocumentsDirectory() path using path_provider why it convert to Unit8list Flutter?

Question

i download this file here for video but it does not save a .mp4 format.it saves as a unit8list. i try to convert it to file then play it into video player.it does not play in videoplayer.file

var url = 'https://www.learningcontainer.com/wp-content/uploads/2020/05/sample-mp4-file.mp4';

Widget of download video. it download successfully. in the path

when i download here img or txt format remain same but not for mp4 file