What's the difference between MOV and MP4?
MOV and MP4 are both containers, and close relatives: MOV is Apple's QuickTime format from 1991, and MP4 (formally MPEG-4 Part 14), standardised in 2001, is built on the same box-based structure that QuickTime pioneered. That shared ancestry is why converting between them is often quick: a container is only the wrapper that holds the video track, the audio track and some timing information. The pictures inside don't have to change.
The difference is reach. Almost every phone, TV, games console, browser, editor and social network accepts MP4 without a second thought. MOV is welcome on Apple devices and in professional editors, but plenty of Windows apps, smart TVs, car screens, web upload forms and older Android galleries either refuse it or play the sound with a black picture.
Why does my iPhone record MOV, and what's inside it?
The iPhone camera saves every video as .MOV because that's Apple's own QuickTime format. What's inside depends on Settings → Camera → Formats. With High Efficiency (the default since iOS 11) the video is HEVC, also called H.265. With Most Compatible it's H.264. The sound is AAC in both cases.
HEVC files are roughly half the size of H.264 at the same quality. Apple's own figures in the Camera settings put 1080p at 30 fps at about 60 MB per minute in HEVC versus 130 MB in H.264, and 4K at 30 fps at 170 MB versus 350 MB. The catch is decoding: HEVC playback on Windows needs Microsoft's paid HEVC Video Extensions, and some older Android phones and smart TVs can't decode it at all.
What happens to the video when you convert MOV to MP4?
The converter reads the file's streams first and then picks the least destructive path:
- H.264 video is copied bit for bit into the MP4. No quality is lost and even a long clip takes seconds.
- HEVC video is also copied, and tagged as 'hvc1' so iPhone, iPad, Mac and Apple TV recognise it in an MP4.
- Anything else, such as ProRes from an iPhone Pro, Motion JPEG from an older camera or Animation codec exports, is re-encoded to H.264 at high quality (CRF 23), because those codecs aren't allowed or supported in MP4 players.
- AAC audio is copied. Other audio, such as uncompressed PCM from some cameras and screen recorders, is converted to AAC at 192 kbps.
- Extra tracks like timecode and metadata tracks, which some MP4 players choke on, are left out. Only the main video and audio are kept.
Why won't the MP4 play after converting?
A copied HEVC stream is still HEVC, now in an MP4 wrapper. That fixes upload forms and apps that reject the .mov extension, but not a device that can't decode HEVC. If an old Windows PC or TV shows sound with no picture, the problem is the codec rather than the container.
The cleanest fix is upstream. Set Settings → Camera → Formats → Most Compatible on the iPhone before recording, or share the video from Photos, which often converts to H.264 for the receiving app. For a file you already have, running it through the Video Compressor on High quality re-encodes it to H.264, which plays everywhere.
Do I need to convert MOV to MP4 for editing?
Most editors (Premiere Pro, DaVinci Resolve, Final Cut Pro, CapCut, iMovie) open MOV directly, so converting isn't needed for editing on a desktop. It helps mainly with web editors and cheaper mobile apps that only list MP4 in their file pickers, and with LMS platforms, job portals and forms that whitelist file extensions.
For upload sites, MP4 with H.264 video and AAC audio is the safest combination there is. YouTube, Facebook, Instagram, TikTok, LinkedIn and X all transcode on their side anyway, so there's no point uploading a bigger file than necessary. If the MOV is huge, compressing it to 1080p first can save a long upload on a mobile connection.
Private by design, even for large files
The conversion runs inside your browser using ffmpeg compiled to WebAssembly. The file is read straight from your disk and the MP4 is written in your browser's memory. Nothing is uploaded, which also means there's no upload queue: a 2 GB file starts converting immediately.
The first conversion downloads the converter itself, about 30 MB, which your browser then caches. After that, converting further files needs no network at all. On phones, the practical size limit is set by memory: a few hundred megabytes is comfortable on a recent iPhone or Android, while multi-gigabyte files are best handled on a laptop.