Why iPhone videos often will not play elsewhere
An iPhone saves video as a .MOV file. When the camera is set to High Efficiency (the default on recent models, under Settings, Camera, Formats), the picture inside is HEVC, also called H.265. HEVC makes files much smaller than the older H.264 at similar quality, but many Windows PCs, older Android phones, smart TVs, video editors and upload forms either cannot play it or ask for an extra codec. MKV files, WebM clips saved from the web, and AVI or 3GP files from older cameras and phones run into the same problem.
MP4 with H.264 picture and AAC sound is the one combination that plays nearly everywhere: iPhone, Android, Windows, Mac, WhatsApp and every major website. That is what this converter makes when you choose MP4, and it puts the file's index at the start (called faststart), so the video can begin playing before it has fully loaded.
Copying versus re-encoding: why some conversions take seconds
A video file is a container (MOV, MP4, MKV, WebM) holding separate streams: the picture and the sound. If those streams are already in a form the new container accepts, there is no need to touch them. The converter copies them across as they are, which takes seconds and loses nothing. When they are not, every frame is decoded and compressed again, which is real work done by your own device. The result tells you which streams were copied and which were re-encoded.
| From | To | What happens |
|---|---|---|
| iPhone MOV, Most Compatible (H.264 + AAC) | MP4 | Copied: seconds, no quality lost |
| iPhone MOV, High Efficiency (HEVC) | MP4 | Picture re-encoded to H.264, sound copied |
| MKV with H.264 and AAC | MP4 | Copied: seconds, no quality lost |
| WebM (VP8 or VP9 with Opus or Vorbis) | MP4 | Re-encoded to H.264 and AAC |
| Anything not already VP8 or VP9 | WebM | Re-encoded to VP8 with Vorbis sound (Opus sound is copied) |
Re-encoding runs on a single processor thread inside the browser, so expect it to take roughly as long as the video plays on a good computer, and longer on a phone.
Keep the video, the picture only, or just the sound
- Video with audio: the whole thing, in MP4 or WebM.
- Video only (no sound): the picture without its sound track. The mute video tool does the same and can also keep the original format untouched.
- Audio only: the sound saved as MP3 or M4A at 128 to 320 kbps. For M4A there is also an "Original" setting that copies the sound exactly when it is already AAC, as it is in most phone videos. The video to MP3 page is set up for just this.
HDR video from newer iPhones
Recent iPhones record HDR (Dolby Vision) video by default. HDR stores a wider range of brightness and colour that most phones, PCs and apps outside Apple's own cannot display properly. The converter turns it into standard H.264 video, which plays everywhere, but it does not perform HDR tone mapping. Bright skies, lights and saturated colours can therefore look a little flatter than they did on the iPhone. For videos you plan to share widely, turning off HDR Video in Settings, Camera, Record Video avoids the issue at the source.
Large files and phones
Files up to 2 GB are accepted. Above 500 MB you will see a warning: it will be slow, and a phone or a computer with little memory may run out partway. If you only need part of a long video, cut it first with the video trimmer, and if the result is too big to send, the video compressor can bring it under 16 MB for WhatsApp or 25 MB for Gmail. Your original file is never changed.
The engine behind this tool
Video and sound are processed by FFmpeg, the open-source engine behind most of the world's video software, compiled to run inside your browser as ffmpeg.wasm. It is downloaded from this site (about 31 MB) the first time you use a video or audio tool, and your browser keeps it for next time. FFmpeg and ffmpeg.wasm are free software, licensed under the GNU General Public License version 2 or later; their source code is at github.com/ffmpegwasm/ffmpeg.wasm.