What is a MOV file?

MOV is a container: a wrapper that holds streams encoded by something else. It is used for editing and broadcast.

The extension is .mov, and the full name is QuickTime Movie. Both matter less than what the file can hold, which is what the rest of this page is about.

Apple published it in 1991. The specification is QuickTime File Format.

A format that has been readable for that long is a format worth trusting with something you want back in ten years.

It is written down and implementable, though the vendor decides what the next version looks like. In practice that is enough for the file to keep opening; it is not enough to be sure of it.

MOV carries an alpha channel, so a logo keeps its soft edges over whatever sits behind it instead of arriving in a white box.

It usually holds H.264, HEVC and ProRes. This is the distinction behind most "why will this not play" questions: two files with the same extension can contain entirely different encodings, and a player that refuses one may be perfectly happy with the other.

It also explains why changing container is often fast and lossless while changing codec is neither. Moving the same stream into a different box rewrites the box; re-encoding rewrites the picture.

MOV can hold several audio tracks and subtitle tracks.

That matters mostly when converting: whatever the target cannot hold is dropped, usually without a warning.

Final Cut Pro, QuickTime Player and Adobe Premiere Pro read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

Only some browsers read it.

Where support is uneven, serving a second format alongside it is the usual answer — the browser takes the one it understands and nobody is left out.

MOV is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

That is the shape of nearly every MOV problem. The file plays flawlessly in QuickTime, in Photos, on the phone that recorded it — and then a colleague on Windows cannot open it, an upload form rejects it, or a video editor imports silence. Nothing is wrong with the file.

MOV is Apple’s container, and Apple’s software fills it with things Apple’s software understands. Some of those things are universal and some are not, and the extension gives no clue which. The first useful question is never about MOV; it is about what is inside this particular one.

QuickTime came first, in 1991. When MPEG standardised a container for the MPEG-4 era in 2001 they took QuickTime’s file structure as the starting point, so MP4 and MOV share their internal organisation almost completely — the same nested boxes, the same track layout, the same index.

The similarity is close enough that a great deal of software will play a MOV renamed to .mp4 and the reverse. That is a fact about how related they are rather than a technique to depend on: it works when the codecs inside happen to be ones MP4 also permits, and fails silently when they are not.

This is the difference that actually bites. MOV can carry ProRes, Apple’s editing codec, which compresses very lightly on purpose so that footage can be cut, colour-graded and re-rendered without accumulating damage. Final Cut and increasingly the iPhone in its professional recording mode produce it.

The cost is size on a different scale from delivery formats. ProRes runs in the region of a gigabyte or two per minute at high definition, so ten minutes of footage is comfortably twenty gigabytes. Nothing outside editing software expects that, which is why such a file will not upload, will not stream and will not attach — and why converting it to H.264 typically shrinks it by a factor of fifty with no visible difference on a screen.

By default, HEVC — H.265 — in a MOV container, because it halves the storage a recording costs. That is a sensible default for the phone and a compatibility problem the moment the file leaves it: older Windows machines, many televisions, several editing programs and a good number of web upload forms do not decode H.265.

The setting that changes this is in the camera options, described as most compatible rather than high efficiency, and it records H.264 instead at roughly double the size. If footage is routinely going to non-Apple machines, changing it once is easier than converting every clip afterwards.

MOV can carry transparency — video with genuinely see-through regions, used for titles, logos, animated overlays and anything meant to be composited over other footage. ProRes 4444 and the Animation codec both support it.

MP4 has no equivalent in general use, so converting such a file flattens the transparency onto a background, usually black, permanently. If a MOV is a graphic meant to sit over something else, it should stay a MOV until the compositing is finished. Converting it first destroys the only property that made it useful.

MOV can hold more than picture and sound: a timecode track for synchronising multiple cameras, several audio tracks for separate microphones, chapter markers, and the orientation flag that keeps a phone video upright.

Most of this survives a conversion to MP4 only partially. Orientation carries over reliably. Multiple audio tracks usually collapse to the first one, and timecode is generally lost. For finished video none of that matters; for footage still in production it is the reason the editor wants the original rather than a converted copy.

Windows has decoded H.264 in MOV for years, so a great many MOV files open without any extra software. The failures cluster on two things: HEVC, whose decoder Microsoft ships as a paid add-on rather than in the box, and ProRes, which the system has never supported at all.

The symptom differs usefully between them. HEVC typically gives an explicit message about a missing codec with an offer to buy one. ProRes more often produces silence, a black frame or an unhelpful generic error, because nothing on the machine recognises the stream well enough to say what it is.

Convert when the video is finished and going to a person: H.264 in MP4 plays on effectively every device made this century and is what upload forms, messaging apps and websites expect. For a ProRes file this is not a compromise, it is the entire point — the editing format has done its job.

Do not convert while editing is still happening. Every re-encode costs a generation, and ProRes exists precisely so that repeated rendering does not accumulate damage. Convert once, at the end, from the highest-quality source you still have.

An upload-based converter has to move the file twice, and a twenty-gigabyte ProRes clip is beyond what most of them accept at all — the size limit exists because their bandwidth is the cost. That rules out exactly the files that most need converting, and it would be dishonest to imply this page rescues them: the free ceiling here is 100 MB per file, 100 files at a time, and a twenty-gigabyte clip is refused at the drop zone rather than converted.

What converting in the browser actually buys is the other thing. Nothing is transmitted, there is no queue, and no daily allowance is spent because none of it runs on our machines — and given that MOV files are overwhelmingly personal footage straight off a phone, that is worth more than the megabytes. For a clip above the ceiling, the honest answer is a desktop tool such as HandBrake or ffmpeg, which also keeps the file on your own machine.