Typical online converters make you upload your video to their servers, wait in a queue, then download the result, which is slow, and a privacy problem for personal or confidential footage. This MOV to MP4 converter is different: the whole thing runs on your own device. Nothing is uploaded, there is no account, and there is no watermark on the finished MP4.
It works for the whole family of QuickTime files: an iPhone MOV to MP4, a screen recording, or a QuickTime export to MP4, and it also accepts MP4, WebM and MKV if you need to normalise those to a standard MP4.