The prefix AgAD is a common characteristic of Telegram's internal file naming convention for media attachments. Because this name is an alphanumeric string generated by a server rather than a descriptive title, the specific content of the video cannot be determined by the filename alone. Technical Profile
Open the file using a versatile media player like VLC Media Player , which handles .mkv files and various codecs natively. AgADkwgAAmRUiFY.mkv
If you did not personally trigger this download or receive it from a trusted contact, exercise caution. MKV files themselves are generally safe, but they are often used to distribute large media files from unknown sources. The prefix AgAD is a common characteristic of