Can you make a video player in App Inventor? Not really, unfortunately.
A question from a reader: Can we make a video player in App Inventor?
The short answer is, unfortunately, not really.
In the App Inventor Designer, in the Palette’s Media section, you can drag a Video Player into the viewer. But this Video Player only plays video files (WMV, MP4) that are stored inside your app (not on the web) and these files are limited to just 1 megabyte in size. Therefore, the Video Player feature in App Inventor is so limited as to not be very useful for most applications.