Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 48)

Downloading and Installing EOS Software or Other
Dedicated Software
Always install the latest version of the software.
Update any previous versions that are installed by overwriting them with the latest version.
Caution
Do not connect the camera to a computer before you install the software. The
software will not be installed correctly.
The software cannot be installed unless the computer is connected to the internet.
Previous versions cannot display images from this camera correctly. Also,
processing RAW images from this camera is not possible.
48