Always ensure the source of compressed files is trusted, as archives can be used to hide malicious software.
The .7z format is used to reduce the file size of the video for easier sharing or storage, or to bundle multiple files together. 335.mp4.7z
You will need archive software such as 7-Zip (Windows), The Unarchiver (macOS), or similar apps on mobile to "extract" or "unzip" the .mp4 file before it can be played in a media player. Always ensure the source of compressed files is
The extension indicates a 7-Zip ( .7z ) compressed file containing a MP4 video file ( 335.mp4 ). The Unarchiver (macOS)