What is M4R?
iPhone Ringtone File
Apple created the M4R format to store iPhone ringtones created with Apple iTunes. You will most likely encounter this format if you transfer a ringtone from a computer to an iPhone. If you don’t know how to open and play M4Rs, check out the associated programs list.
The M4R file type is based on the widely supported MPEG-4 Part 14 specification. This audio format supports copyright protection. The playback of protected M4R files is not possible on any non-Apple device. However, if the M4R file isn’t copy-protected, you can open it with almost any player.
iTunes, QuickTime Player, Windows Media Player, and VLC