MOV is Apple's QuickTime container format, introduced in 1991. MP4 is an international standard (ISO/IEC 14496-14) based on MOV, formalized in 2001. They are closely related formats that share the same internal structure (the ISO Base Media File Format). The difference between them is smaller than most people think.
Why iPhones use MOV
Apple's ecosystem has used QuickTime since the early 1990s. MOV is the native container for Apple's video tools: iMovie, Final Cut Pro, QuickTime Player, and the Camera app. When iPhones record video, they package it as MOV because Apple's entire software stack is optimized for that container.
The video codec inside the MOV container is usually H.264 (in "Most Compatible" mode) or H.265 (in "High Efficiency" mode). The audio codec is typically AAC. These are the same codecs used inside MP4 files.
Why Windows sometimes has trouble with MOV
Windows Media Player historically did not support MOV without installing QuickTime. Modern Windows (10 and 11) handles MOV files better because it includes HEVC and H.264 decoders. However, some Windows applications (older video editors, business software, web upload forms) still reject MOV files because they check the file extension rather than the actual content.
The fix is converting MOV to MP4. Since both containers typically hold the same codecs (H.264/H.265 video, AAC audio), the conversion can be done by simply repackaging the streams in an MP4 container without re-encoding. This is called remuxing.
Remuxing vs. re-encoding
Remuxing: The video and audio streams are copied from the MOV container to an MP4 container without any processing. The output file contains bit-identical video and audio data. Zero quality loss. The process takes seconds regardless of file length.
Re-encoding: The video is decoded and re-encoded into the MP4 container. This takes longer and introduces one generation of quality loss. Re-encoding is only necessary when the codecs inside the MOV are not compatible with MP4 (rare for modern recordings).
For iPhone MOV to MP4 conversion, remuxing works in most cases. The H.264/H.265 and AAC streams inside the MOV are fully compatible with the MP4 container.
When re-encoding is necessary
Some older MOV files use codecs that are not supported in MP4 containers:
- ProRes (used by professional cameras and Final Cut Pro): Not natively supported in MP4. Must be re-encoded to H.264 or H.265.
- Apple Intermediate Codec: Legacy codec from older Mac video tools. Must be re-encoded.
- Sorenson Video: Very old QuickTime codec from the late 1990s. Must be re-encoded.
For modern iPhone and iPad recordings that already use H.264 or HEVC video with AAC audio, the MediaBrew format conversion tool remuxes directly into an MP4 container without re-encoding, finishing in seconds with zero loss of quality.