If you are looking for a specific video described by this name:
Browsers often rename video fragments (blobs) using random alphanumeric strings during playback. 2. How to Open the File 3453453451b.mp4
You can use a tool like ExifTool to see the "Date Created" or "Software" tags, which might tell you exactly which app or camera generated the name "3453453451b." 4. Searching for the Content If you are looking for a specific video
If you downloaded this file from an untrusted source, run it through VirusTotal before opening. While .mp4 files are generally safe, they can occasionally exploit vulnerabilities in outdated media players. Searching for the Content If you downloaded this
Discord renames uploaded files with long numerical strings. If you found this in a cache folder, it is likely a video shared in a server you frequent.
If you have the file but it won't play, it may be corrupted or missing its header.