How this MOV to MP4 converter works
MOV is the container used by QuickTime and by many iPhone recordings, and some MOV files do not play on Windows, Android or in web players. When the video is already H.264, VimCut copies it into an MP4. HEVC and other codecs are re-encoded to H.264 with AAC audio, which plays almost everywhere.
Only the first video and audio stream are kept, and a re-encoded file uses the yuv420p pixel format so it stays playable on every device. The MP4 is laid out so it can begin playing before it has fully loaded. When your browser supports it, the work uses the built-in hardware video encoder. Otherwise it falls back to WebAssembly (ffmpeg.wasm), which is slower but gives the same kind of result. A progress bar shows how far the conversion has got, and your original MOV file is never changed.