MOV to MP4

A MOV file and an MP4 file are usually the same recording in two different wrappers. This tool takes the wrapper off and puts an MP4 one on, copying every compressed video and audio packet across untouched. There is no re-encoding step, so there is nothing to lose: the picture that comes out is bit-for-bit the picture that went in.

Why MOV and MP4 are so often the same file underneath

Apple designed the QuickTime File Format in the early 1990s. When MPEG needed a container for MPEG-4, it took QuickTime as the starting point. The result is that MOV and MP4 share the same internal structure — a tree of boxes with four-letter names like moov, trak and mdat — and the same way of describing tracks, timing and codecs. The main difference is a short brand field near the start of the file that says which specification it claims to follow.

That is why converting between them does not need to touch the video. The compressed frames are already in the layout MP4 expects. What changes is the label on the outside and a handful of bookkeeping boxes. This is called remuxing, and it is a completely different operation from transcoding, which means decoding every frame and compressing it again.

The practical consequence: this page finishes in milliseconds rather than minutes, your file does not get bigger or blurrier, and running it twice does not degrade anything. A 6-second 720p clip takes about 13 ms here. A minute of 1080p takes about 87 ms, which works out to roughly 500 MB of media moved per second.

What actually goes wrong with MOV files, and what does not

It is tempting to say browsers cannot open MOV. That is not true — Chromium-based browsers play plenty of MOV files perfectly well, even though the standard feature-detection call for the format returns an empty string. So if a MOV plays in your browser but is rejected somewhere else, the browser was never the problem.

The real friction is elsewhere. Upload forms, learning platforms, ad networks, smart TVs, Android phones and a lot of Windows software check the file extension or the brand field and refuse anything that is not MP4, regardless of what is inside. Video editors on Windows are the same. Renaming the file does not fix it, because the brand field inside still says QuickTime. Rewriting the container does fix it, and that is what this page does.

There is one case this tool honestly cannot solve. Some MOV files from professional cameras and editing suites contain ProRes, DNxHD or the QuickTime Animation codec. Those are not codecs MP4 has a slot for, so there is no wrapper change that makes them into a playable MP4 — the only route is a real re-encode. If we cannot identify a track well enough to move it safely, the page says so instead of producing a file that looks fine and plays wrong.

iPhone recordings, HEVC, and why no decoder is needed

Since iOS 11 an iPhone records video as HEVC (also called H.265) inside a MOV container, because HEVC gets similar quality at roughly half the bitrate of H.264. That is also the main reason people end up here: the file plays on the phone and then nothing on the desktop will take it.

HEVC rewraps exactly like H.264 does. Copying a compressed packet from one container to another never decodes it, so this page does not need an HEVC decoder to do the work — and we verified that rather than assuming it, by counting decoder instantiations during a run and by repeating the run with HEVC decoding switched off. The packets came out identical both times.

One consequence is worth stating plainly, because it looks like a failure when it is not. If your device has no HEVC decoder, nothing on that machine can show you the picture — this page included. A player in that situation reports the right duration, plays the sound and shows a black rectangle, which is indistinguishable from a broken conversion. So the page checks for the decoder before you start and tells you, instead of handing you that rectangle to interpret. The file itself is complete and correct: open it in QuickTime, VLC, Photos, or on the phone it came from.

If what you actually have is an iPhone photo rather than a video, the equivalent tools are HEIC to JPG and HEIC to PNG, which work the same way — in your browser, with nothing uploaded.

How to check that nothing was re-encoded

Every conversion here reports how many video and audio packets it copied. A packet is one compressed unit — for video, normally one frame. If the count matches the source and the operation took a few milliseconds, no encoder ran: encoding a minute of 1080p in a browser takes over twenty seconds, roughly 250 times longer than copying it.

For a stronger check, compare the media data itself. Tools such as ffprobe can print a hash of each packet, and for a rewrap the hashes match one by one. That is exactly how this page was validated before it shipped, because the softer checks are not good enough: a file that has been quietly re-encoded still plays, still reports the right duration and still passes a codec check. Only comparing the bytes tells them apart.

The privacy side is checkable in the same spirit. Open your browser developer tools, switch to the Network tab and run a conversion. Your file appears in no request, because there is no server to receive it. The Content-Security-Policy header this site sends restricts connections to our own origin, so your browser would block an attempt to send it even if a script tried.

Practical limits

We impose no file size cap, no daily quota, no watermark and no account. The real ceiling is your device: the finished file is assembled in memory before you download it, so allow for roughly the output size plus a hundred megabytes of working space. On a desktop, files up to about 500 MB are comfortable. On a phone, halve that.

The page warns you when a file is above that mark instead of letting the tab die silently. It is still worth trying — the limit is a guideline, not a wall — but if the tab reloads, that is the reason. A save-straight-to-disk mode for multi-gigabyte files is not built yet, and we would rather say so than imply a capacity we have not shipped.