MOV to MP4: Making iPhone and Mac Video Play Everywhere

MOV is Apple's QuickTime container and MP4 is the ISO base media container. They are close relatives, and both can hold H.264 or HEVC video with AAC audio. That is why a MOV recorded with H.264 can often be rewrapped into an MP4 with the video and audio streams copied byte for byte: no decoding, no re-encoding, no generation loss, and the conversion finishes in seconds even for a large file.

When people say a MOV will not play, the codec is frequently the real culprit. Newer iPhones record HEVC by default, and HEVC inside a MOV will not play on many Windows machines, Android devices or browsers even after the container is changed to MP4. In that case the video must be decoded and re-encoded to H.264, which is slower and costs one generation of quality.

Check the codec before converting. On a Mac, the Finder's information panel or QuickTime's inspector shows it; on Windows, the file's properties do; command-line tools such as ffprobe report it directly. If the video is H.264, choose a converter that copies the streams. If it is HEVC or ProRes, expect a real re-encode and budget time accordingly — ProRes in particular produces very large intermediates and takes a while to decode.

The audio matters too. QuickTime can carry uncompressed or unusual audio that MP4 players reject, and a stream copy that includes incompatible audio produces a file that opens but has no sound. Converting the audio to AAC while copying the video is a good compromise: the video stays untouched and the audio loss is inaudible.

A re-encode applies lossy compression to an already compressed source. At a generous bitrate the difference is hard to see; at a low one the artefacts of the first encode get compressed again and the result looks worse than either input. Set the output bitrate close to the source's, or use a quality-based setting that targets visual quality rather than a fixed size.

Watch the resolution as well. A 4K phone video re-encoded at 1080p is a deliberate, often sensible reduction for sharing, but it is irreversible. Keep the original MOV as the master, and treat the MP4 as the delivery copy. The same applies to frame rate: 60 fps to 30 fps halves the data and changes the look of motion, so only do it when the destination or file size demands it.

Phone video often carries a rotation matrix rather than being physically rotated. A converter that drops the metadata produces a video that plays sideways, which looks like a bug in the player. Most modern tools apply the rotation during re-encode and preserve it during a remux, but it is worth checking the first frames of the output rather than assuming.

For the web, the container change alone is not enough: a video served for progressive playback should have its index at the front of the file so the browser can start before the download finishes. If a page shows a spinner until the whole clip is fetched, the file is fine and its layout is not. Also confirm the audio track survived; a silent video on a website is a common and quiet failure.