The extension indicates a Matroska Video file. It is not a video codec itself but a "multimedia container" that can bundle an unlimited number of video, audio, picture, and subtitle tracks into a single file.
Telegram often displays MKVs as "files" rather than playable "videos" in the chat interface because they may use codecs (like DTS audio) that the app's built-in player cannot decode. AgAD0gADBUChVw.mkv
It is open-source and highly flexible, supporting high-quality features like multiple audio languages and chapter points, which is why it is often used for high-definition movies and TV shows. Common Issues with Telegram MKVs The extension indicates a Matroska Video file
The cryptic name "AgAD0gADBUChVw" is often replaced by users with more descriptive titles using Telegram Rename Bots to make the file easier to find later. It is open-source and highly flexible