The .mkv extension indicates it is a Matroska Video file, which is a high-definition container format capable of holding multiple audio tracks, subtitles, and high-quality video. How to Identify the Actual Content
If you still have the chat, look for a video file sent around the time this file was created. AgADtAIAAkXhEEQ.mkv
This specific naming convention ( AgAD... ) is a unique file ID generated by Telegram. AgADtAIAAkXhEEQ.mkv
Use a player like VLC Media Player or MPC-HC , which are designed to handle .mkv files regardless of their filename. AgADtAIAAkXhEEQ.mkv
Right-click the file and select Properties (Windows) or Get Info (Mac). Sometimes the "Details" tab will contain the original title or tags.