(e.g., Was it sent in a specific Telegram group or found on a hard drive?)
(e.g., Is it a security recording, a lecture, or a personal video?) AgADCQgAAjVlyVY.mkv
If you have access to the file, information like the file size , duration , or creation date could help narrow down what it might be. Is it a security recording
Based on the alphanumeric string (e.g., "AgADC..."), this looks like a often used by messaging apps (like Telegram ) or cloud storage platforms to name uploaded files. What you can do next: information like the file size
If this file is from an unknown source, do not open it . MKV files can occasionally be used to hide scripts or malware if the media player has vulnerabilities.