Use QuickTime Player , which natively supports MP4 files.
For a Mac, QuickTime supports MP4 and on Windows, you can use Windows Media Player. How to play MP4 files in Windows - Microsoft Support 0ha8sap1ng2b6ys7wpf02_source.mp4
Right-click the file and select Open with > Windows Media Player . Use QuickTime Player , which natively supports MP4 files
If you are trying to turn this clip into a short-form "feature" (like a TikTok, Reel, or YouTube Short), you can use free tools to add music, captions, and effects: Use QuickTime Player