Because Instagram does not provide a native "Download" button for Reels or Feed videos, users turn to external tools. Tools like yt-dlp or Instaloader allow users to archive content, often defaulting to these numeric filenames unless manually configured to include captions or dates. Digital Organization and Challenges

The string is not arbitrary; it is likely a Unix timestamp in milliseconds, which translates to a specific moment in time (likely late 2022). Instagram and various Instagram downloaders use these identifiers to ensure every saved file has a unique name, preventing file collisions .

Ultimately, a file like "Download instagram 1666316460372.mp4" is a placeholder—a digital vessel for a piece of content that was once fleeting but has now been captured for offline viewing. How does Instagram name files - Stack Overflow

A numeric string (like 1666316460372) generated by Instagram’s backend or a downloader’s script to track specific media.