Native apps like Photos or the default player do not reliably support MKV. Use third-party apps like VLC for iOS to watch it.
MKV files are generally high-quality but may not play natively on all devices. AgADbQoAAg3LCFc.mkv
You can often play these directly, though certain codecs may require you to save the file to your computer first. Management & Organization Native apps like Photos or the default player
While many modern Android players support MKV, you may need VLC for Android if your default gallery app fails. which can hold multiple video
[Feature Request] Preserve the original file names #24318 - GitHub
The .mkv extension indicates a Matroska Multimedia Container , which can hold multiple video, audio, and subtitle tracks in a single file.