Renaming recording.anydesk to recording.mp4 will never work. You must (transcode/remux) it properly.
If conversion fails:
Several commercial tools claim to support "AnyDesk to MP4." Be cautious: Most generic video converters cannot parse the .anydesk container. As of 2026, only two dedicated tools work reliably: Convert Anydesk Video To Mp4 -UPD-
Use FFmpeg 7.3+ with the command template in Section 4.1. It is free, fast, and now handles AnyDesk v9.2+ recordings (including encrypted streams if you have access to the recording key from the AnyDesk client that generated the file). Renaming recording