Having two .mp4 extensions typically happens in one of three ways:
A user manually renamed the file to include ".mp4" without realizing the system already added it. 9447939.mp4.mp4
This numerical string is likely an internal ID or serial number assigned by a specific platform, camera, or automated system (e.g., a security camera or a content management system). Having two
Use a tool like ExifTool if you need to see technical "buried" comments or encoding dates that standard players might hide. or automated system (e.g.
Based on the standard, a file with this extension generally possesses the following traits: