Generic hashed filenames like this are sometimes used to distribute malicious content or phishing links.
If you received this from an unknown email or a suspicious link, do not run the file. a99facc6b4c619967c93b2ff9934c44c.mp4
Upload the file to sites like Metadata2Go or Pics.io Video Metadata Viewer to see the resolution, frame rate, and sometimes even GPS location or camera model. Generic hashed filenames like this are sometimes used
You can use tools like VirusTotal to see if the file has been flagged for malware or if it exists in their database of known file hashes. a99facc6b4c619967c93b2ff9934c44c.mp4
If you found this online, the alphanumeric string a99facc6b4c619967c93b2ff9934c44c is often used by servers to prevent duplicate files or to hide the original filename.