What is the MKV format
MKV is a highly flexible multimedia container that can store video, audio, subtitles and multiple tracks in a single file. For that reason it is common in high-quality content, media collections and files where extra information needs to be preserved alongside the main video.
However, not every device or service handles MKV in the same way. Converting MKV to MP4 is often useful when simpler and more reliable playback is needed on phones, TVs, browsers, video platforms and apps with more limited support.