There is only one file type that uses the .MOTN extension:
Apple Motion Generator Project Template
A MOTN file is a project template that contains a generator created by Apple Motion, a motion graphics application. It stores information about a generator, which includes the duration and placement of the generator. MOTN files do not contain the actual media that makes up the generator only references to the media.
Generators are graphics designed to enhance video, such as a colored background, animated or static pattern, or gradient. They can also include text characters for countdown animations or timecode.
Apple Motion uses several extensions for saving different project types. Titles created in Motion are saved as .MOTI files, effects are saved as .MOEF files, and transitions are saved as .MOTR files.
By default, MOTN files are saved in the following directory in macOS:
MOTN files are commonly found in the "Generators" folder accompanied by two .PNG thumbnail previews, a .MOV preview of the MOTN generator, and a media folder that stores all the media associated with the generator project.
Apple Motion is used to create generators, effects, transitions, and titles for video projects. It is typically used alongside a video editor to create an effect, title, transition, which is then exported and imported into the video editor. Motion is most commonly used with Final Cut Pro because of its similar appearance and integration with the video editor.
Updated: January 14, 2018