Convert MOV to MP4

Almost every MOV that reaches a converter was made by the person converting it. An iPhone records to .mov and always has. A Canon, Sony or Blackmagic camera writes MOV onto its card. Final Cut Pro, iMovie and QuickTime Player all export it. Nobody downloads a MOV; they film one, or they make one, and then they try to do something with it.

The something is where it stops. A Windows PC plays it or does not depending on the codec. An Android phone opens it or shows a black rectangle. An upload form lists MP4, MOV and AVI and then rejects the MOV anyway because the list was written for a validator that checks the extension and a decoder that does not agree with it. All of those are fixed by producing an ordinary MP4, which is why this is the busiest conversion the format has.

Since iOS 11 an iPhone has two recording settings, and the one it ships with is High Efficiency. That writes HEVC, also called H.265, which halves the file size and is not decodable everywhere. The other setting, Most Compatible, writes H.264 and produces files roughly twice as large. Both of them are called .mov, which is why the extension gets the blame.

You can test which one you have in about ten seconds: if the file plays in the Photos app on the phone and shows a black frame or asks for a codec on a Windows machine, it is HEVC. The MP4 written here is always H.264 at High profile, so it removes that question permanently. If you would rather not convert anything again, changing the camera setting to Most Compatible stops the problem at the source for everything you film afterwards.

It is the first thing people try and it fails more often than it works. A QuickTime file announces itself in the first few bytes with a brand code of "qt ", and a strict MP4 reader looks at that brand and declines. Some players sniff the contents and forgive the mismatch; validators on upload forms, set-top boxes and older editing software do not.

This site is strict in the same way, deliberately. A file handed to the MP4 page is opened with an MP4 reader and a file handed to this page is opened with a QuickTime one, so a renamed MOV fails on the wrong page rather than converting quietly into something mislabelled. If the extension were the whole problem, the honest advice would be to rename it — and for this pair it is not.

H.264 at High profile for the picture and AAC for the sound, in every case, whatever the MOV held. That pairing is chosen rather than inherited: it is the one combination that decodes on televisions, in browsers, on both phone platforms and in every editor, which is the entire point of the exercise.

The encode is 8-bit. H.264 High profile carries eight bits per colour channel, so a 10-bit recording — HDR video from a recent iPhone, or log footage off a camera — is flattened on the way through. For a clip that is going to a phone, a messaging app or a form, nobody will see the difference. For a graded master you intend to keep, keep the MOV as well.

A phone camera sensor is landscape no matter how you hold the phone. A portrait video is therefore recorded as a landscape picture with a note attached saying "rotate this ninety degrees on the way to the screen". That note is why the same file looks correct in Photos and sideways in some desktop players.

MP4 can carry that note, so this conversion passes it across unchanged and the MP4 behaves exactly as the MOV did. If you also choose a resolution, the picture is rotated for real during the re-encode and the note is no longer needed — which is the more robust outcome if the file is going somewhere you do not control. Converting the same clip to MKV or WebM always takes the second route, because Matroska’s own rotation field is ignored by too many players to rely on.

The free tier accepts files up to 100 MB, and video is the one category where that is a real constraint rather than a formality. Apple prints the recording rates in Settings under Camera and then Record Video: roughly 170 MB a minute at 4K and 30 frames a second in High Efficiency, and about 65 MB a minute at 1080p. That makes the ceiling around thirty-five seconds of 4K, or a minute and a half of 1080p.

The practical answer is to trim first rather than to convert first. Both the iPhone Photos app and the Windows Photos app can shorten a clip without re-encoding it, and thirty seconds of the part you care about converts in a fraction of the time a full recording would. If you genuinely need the whole thing, a desktop tool is the right instrument and there is no point pretending otherwise.

Resolution is the largest saving on offer and it is a separate control from quality. Dropping a 4K recording to 1080p removes three quarters of the pixels, and the encoder then spends its budget on the ones that are left — the result is usually both smaller and cleaner than the same bitrate spread across four times the area.

The list only ever goes down. Asking for 4K from a 1080p clip is ignored, because upscaling adds bytes and no detail. Choose 1080p for anything being sent to a person or a form, 720p for a messaging app, and leave it at the original size only when the MP4 is replacing the MOV as the copy you keep.

MOV is a container with a wide door. Alongside H.264 and HEVC it commonly holds ProRes, which is what Final Cut Pro, an Atomos recorder or a cinema camera writes, and no browser decodes ProRes. A ProRes MOV handed to this page stops with a message saying nothing in the file could be converted and that it may use a codec this browser cannot read — which is accurate, and is a decoder problem rather than a fault in the file.

The same applies to anything else exotic that a professional workflow puts in a QuickTime wrapper. The route for those files is the software that made them: export H.264 from Final Cut or Premiere directly, or run the file through a desktop transcoder. Nothing in a browser can shortcut a codec the operating system does not have.

Only the picture and the sound cross over. QuickTime files from cameras and editing software frequently carry a timecode track, subtitle tracks, chapter marks and camera metadata, and none of those are read — the conversion sees video and audio tracks and nothing else. For a phone clip going to a relative that costs nothing. For a camera original with timecode you intend to conform later, it is a reason to archive the MOV rather than replace it.

Creation date is worth its own sentence, because people lose it and then blame the converter. The MP4 is a new file with a new timestamp, so a folder sorted by date will not match the order things were filmed in. Copy the originals somewhere before converting a whole card, and treat the MP4s as the shareable version rather than the record.

This is the conversion where the privacy argument stops being abstract. The files are birthdays, hospital visits, children, houses, number plates and conversations that were never meant to leave the phone, and the ordinary way to convert one is to upload several hundred megabytes of it to a site chosen from a search result.

Here the decoding and the encoding both happen in the tab, using the same hardware codecs the phone or laptop already uses to play the video back. You can confirm it by opening the network tab and converting something — nothing carrying the file goes out. The side effect is speed: a large recording converts as fast as your machine manages rather than as fast as your connection uploads it, which for a hundred megabytes is usually the bigger number anyway.