Cloud Convert handles the conversion on their website, making it an accessible option for basic video format changes. However, for larger files or more advanced needs, I recommend using VLC media ...

You can convert files to the MP4 format on the VLC media player, making them more accessible across your devices.

VideoLAN's VLC software includes an interface that helps you convert a video file to MP4 format, after which you can upload it to your preferred site or save it on your favorite mobile device.

For example, to convert a MKV file to MP4 to be able to play it directly on your Mac, you’d simply launch Movavi and drag and drop the MKV file into the window. Then, you select MP4 output.