C3D - Coordinate 3D File is a file extension that is always stored in C3D format. It can always be used for saved biomechanical information. You can also use this extension when it comes to storing three dimensional motion capture data. You can also use this extension when it comes to standard formats. It was mainly designed for data storage and lets user’s store and change custom parameters. There is also a main resource for the C3D format which can be accessed by going to C3D.org. This format and extension comes in handy when you really need it the most.