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In the mov vs mp4 question, the extension is not what makes one file twice the size of the other. Both are containers: wrappers that hold a video track, an audio track and some metadata. Put the same tracks in either wrapper and the two files come out almost exactly the same size.
So when your MOV is 400 MB and the MP4 of the same clip is 200 MB, something inside is different: the codec, the bitrate or the sound. This guide shows how to tell which, and which format to pick.
MOV vs MP4: which file is smaller?
Neither, by itself. The container adds a small index and some metadata, a tiny fraction of the file. Everything else is the video and audio data, and that data is the same size whichever wrapper it sits in.
In practice MP4 files are often smaller, for a reason that has nothing to do with the format. A MOV usually comes straight from a camera, an iPhone or an editing app, at a high recording bitrate. An MP4 has usually been exported, uploaded or sent through an app that compressed it harder on the way.
The short answer
The same video and audio tracks take the same space in MOV and in MP4. A big size gap means the two files were encoded differently, not just packaged differently.
What is a MOV file?
A MOV file is a video in Apple's QuickTime File Format, introduced with QuickTime in 1991. It stores video, audio, subtitles and timecode as separate tracks, each made of small labelled blocks called atoms. Apple documents the structure in its QuickTime File Format reference.
You meet MOV files in three places: iPhone and iPad recordings, screen recordings made on a Mac, and exports from editing apps such as Final Cut Pro. Many cameras write MOV too.
MP4 came later and is a close relative. The ISO standard behind it was built on the QuickTime format, which is why the two share the same track and atom layout. The MDN guide to media container formats lists what each one can carry.
What is the difference between MOV and MP4?
The real difference between MOV and MP4 is who controls the format and which codecs each one is expected to carry. The structure is nearly the same.
| Point | MOV | MP4 |
|---|---|---|
| Made by | Apple, as the QuickTime format | ISO, as an international standard |
| Usual video codecs | H.264, H.265 (HEVC), ProRes | H.264, H.265 (HEVC), AV1 |
| Usual audio | AAC or uncompressed PCM | AAC |
| Where it comes from | iPhones, cameras, Mac screen recordings, editors | Exports, downloads, messaging apps, the web |
| Plays on | Apple devices and most editing apps | Nearly every device, browser and TV |
| Effect on file size | None by itself | None by itself |
The codec row is the one that matters for size. A codec is the method that squeezes the picture, and it decides far more than the container does. If the term is new, what is a codec explains it from the start.
Why is a MOV file bigger than the same MP4?
Three things inside the file explain almost every size gap. Check them in this order.
The video codec is different
H.265, also called HEVC, needs roughly half the bitrate of H.264 for similar quality. So the same clip saved once with each codec can differ by a factor of two, in either direction.
This is the classic iPhone case. With the camera format set to High Efficiency, an iPhone records H.265 inside a MOV. Convert that clip to an H.264 MP4 at the same quality and the MP4 is the bigger file. Apple describes the two camera modes in its guide to HEIF and HEVC media.
ProRes is the opposite extreme. It is an editing codec that keeps every frame nearly intact, and it takes gigabytes per minute. ProRes lives in MOV files, so a ProRes MOV dwarfs any MP4 of the same footage.
The bitrate is higher
File size is bitrate multiplied by length. One minute at 50 Mbps is about 375 MB. The same minute at 8 Mbps is about 60 MB, in MOV or in MP4.
Cameras record at high bitrates on purpose, to leave room for editing. An iPhone lists about 400 MB for one minute of 4K at 60 fps in Settings > Camera > Record Video. An MP4 that went through a messaging app or an export preset was squeezed to a fraction of that.
The audio is uncompressed
Cameras and editors often write uncompressed PCM sound into a MOV. Stereo PCM at 48 kHz and 16 bits takes about 11.5 MB per minute. AAC at 192 kbps, the usual MP4 sound, takes about 1.4 MB per minute.
On a long, low-bitrate video such as a screen recording, that audio alone can be a large share of the file.
MP4 vs MOV: which plays on more devices?
MP4 does. An MP4 with H.264 video and AAC sound plays on practically every phone, computer, browser, TV and upload form made in the last decade.
MOV plays everywhere in the Apple world: Photos, QuickTime, iMovie, Final Cut Pro and Safari. Outside it, results vary. Some Windows and Android players open a MOV without complaint, others refuse, and many websites only accept MP4 uploads.
Watch the codec here too. An H.265 clip can fail on an older Windows PC whether it is a MOV or an MP4, because the machine lacks an HEVC decoder. In that case changing the container fixes nothing. Changing the codec to H.264 does.
MOV or MP4: which should you use?
Pick by where the video is going, not by which one sounds more professional.
Sending, uploading or posting
MP4 with H.264
It opens on the other person's device without questions.
Staying on iPhone and Mac
MOV with H.265
It is what the iPhone records, and it keeps HDR.
Editing in Final Cut Pro or similar
MOV
It carries ProRes and uncompressed sound, which editors prefer.
Publishing on a web page
MP4
Every modern browser plays H.264 in an MP4.
If the only problem is size and the MOV already plays where you need it, keep the format and lower the bitrate instead. The MOV compressor takes one MOV up to 1 GB, re-encodes the video with H.264, H.265 or AV1 at the quality and resolution you choose, copies the sound as it is and hands back a MOV.
Can you turn a MOV into an MP4 without losing quality?
Yes, when the codecs inside are ones MP4 accepts, such as H.264 or H.265 video with AAC sound. The tracks are copied into the new wrapper untouched. This is called remuxing, it takes seconds, and the file size barely changes.
With the free command line tool FFmpeg it is one line:
ffmpeg -i input.mov -c copy output.mp4The same idea is explained step by step for another container in converting MKV to MP4 without re-encoding. If the MOV holds ProRes video or PCM sound, a plain copy will not give you a file that plays widely, and those tracks need re-encoding.
Re-encoding is what the video converter on this site does. Drop a MOV up to 100 MB, leave Output format on MP4 and Codec on H.264, and download a file that opens on Windows, Android and most players. The sound is copied when MP4 can take it and re-encoded to AAC when it cannot.
Two things to know before you use it. The quality is fixed, so the MP4 can come out larger or smaller than the MOV. An H.265 iPhone clip often grows, because H.264 needs more data for the same picture. And Resize (height) offers 1080p, 720p and 480p if you want a smaller result.
Renaming the file is not converting
Changing .mov to .mp4 by hand sometimes works, because the two formats are so alike. It changes nothing inside the file, so a player that could not decode the video before still cannot.
Video converterTurn a MOV into an H.264 MP4 that plays almost everywhereMOV compressorMake the MOV smaller and keep it a MOVFrequently asked questions
No. Quality comes from the codec and the bitrate, not from the container. A MOV and an MP4 holding the same H.264 or H.265 track look identical. MOV files often look better only because they tend to be camera originals at a high bitrate, while MP4 files have usually been compressed again.
The iPhone camera saves video as MOV, with H.265 in High Efficiency mode or H.264 in Most Compatible mode. The size comes from the recording bitrate: Settings > Camera > Record Video lists about 400 MB per minute for 4K at 60 fps. A lower resolution or frame rate records smaller files.
Only if the video is re-encoded at a lower bitrate or with a more efficient codec. Copying the tracks into an MP4 leaves the size almost unchanged. Re-encoding an H.265 MOV to H.264 at the same quality can even make the file bigger, since H.264 needs more data for the same picture.
Often, but not always. A MOV with H.264 video opens in many Windows players. A MOV with H.265 video needs an HEVC decoder that some Windows PCs do not have, and a ProRes MOV needs editing software. An H.264 MP4 is the safe choice when a file has to open on any Windows machine.
Large platforms such as YouTube accept both and re-encode whatever you upload, so the container does not change the final quality. MP4 with H.264 is still the safer upload, because smaller sites, forms and messaging apps often accept only MP4, and the file is usually smaller and quicker to send.