MPEG-4 Ringtone (.m4r)
The M4R file extension, standing for "MPEG-4 Ringtone", is a specialized audio format introduced by Apple in 2007 for iPhone ringtones. M4R files are essentially AAC-encoded audio files stored in the MPEG-4 container format, similar to M4A files but specifically designed for ringtones. These files are typically created using iTunes or third-party software and are limited to a maximum length of 40 seconds to comply with iPhone ringtone requirements. Historically, users would sync M4R files to their iPhones via iTunes, but they can now be transferred using various file management tools.