A MOV file and an MP4 file are almost the same thing: both are boxes of the same shape holding video and audio streams. The difference is what is inside. iPhones and Macs often put HEVC (H.265) video into a MOV, and HEVC is what Windows, Android and most web players refuse.

What the conversion does

Convert Files re-encodes the video to H.264 and the audio to AAC, then writes an MP4. That pair plays on essentially every device, TV, browser and messaging app. It is a real re-encode: every frame is decoded and encoded again inside your browser, so a two-minute clip takes a minute or two and the tab has to stay open.

Settings that matter

• Width — leave at 0 to keep the size, or set 1280 for a much smaller file that still looks good on a phone
• Frames per second — 30 is right for almost everything; 60 doubles the work for sports and games footage
• Quality — 85% is the sweet spot; lower if the file must be tiny

WebM instead?

If the video is going onto a website you build, .webm (VP9 + Opus) is usually smaller than MP4 at the same quality and is supported by all modern browsers. For anything else, MP4.

Only the audio? Choose .mp3 or .m4a as the target and the video track is dropped entirely.