mp4 from player doesn't play on recipient's pc or mac

[fixeighted]

As the title, does anyone have any idea of why this would be true?
I simply output to mp4 with default settings and it plays locally but
not when sent to others.

[yolov]

What are they trying to use for opening mp4 files on their end?
Player uses ffmpeg to read and encode mp4 files. FFmpeg and/or any application that uses it should do fine. For example VLC for PC, or even the built-in media player in Windows. For mac - they can use quick time.

Edit: player always encodes mp4 with H-264 encoding (the most popular one) if that helps in any way.

[fixeighted]

I use VLC so no issues. I sent the guy your response, so it's up to him to sort out now
He should know to at least experiment but y'know...some people!