The "(1)" in the filename usually indicates it is a duplicate download. You can safely rename it to something more descriptive while keeping the .mp4 extension. How to play MP4 files in Windows - Microsoft Support
Double-click the file to open it in QuickTime Player . shinx14847 (1)mp4
If your default player fails, try the VLC Media Player , which includes codecs for nearly every type of MP4 encoding. The "(1)" in the filename usually indicates it
MP4 is one of the most common formats for streaming and downloading because it compresses high-quality video into a relatively small size. try the VLC Media Player
Use File Explorer to locate the file, right-click it, and select Open with to choose a player like Windows Media Player or VLC.