Only open files from trusted websites. Generic names like downloadfile.mp4 are sometimes used by malicious sites to hide the file's true content.
Most modern devices can play MP4s using the default media player . downloadfile.mp4 (2)
Many websites use a generic downloadfile.mp4 name for videos rather than a descriptive title. Only open files from trusted websites
Use antivirus software or an online scanner before opening a file with an ambiguous name. downloadfile.mp4 (2)
If it won't play, you can use tools like VLC Media Player to convert it to a different format.
If the file is only a few kilobytes, it may be a broken link or a shortcut rather than the actual video. How to Manage the File