m4r
What is a .m4r file?
audio/mp4
M4R is an Apple ringtone format that is technically an M4A/MP4 audio file with a renamed extension recognized by iOS and iTunes as a ringtone. It contains AAC audio, typically a short clip. The distinct extension is used purely to categorize the file as a ringtone.
How to use a .m4r file
Use an example M4R to test ringtone import workflows, verify that MP4 audio parsers handle the alternate extension, and exercise converters that produce iOS ringtones.