Right-click, select Properties , and go to the Details tab.
If you saved a Live Photo as a video, it often adopts a timestamped name similar to this. 3. Contextual Content Video Dec 21, 10 09 54 AM.mp4
Right-click the file and select Get Info . Look under "More Info" for dimensions, codecs (usually H.264 or HEVC), and duration. Right-click, select Properties , and go to the Details tab