State the destination’s real requirement
Before exporting, identify what the receiving application or device actually accepts. A request for an MP4 file is a container requirement, while a request for H.264 describes compression. Keep those different properties separate so a filename change is not mistaken for conversion.
Use a short authorized sample and preserve the original. Decide which audio and other content must remain. A smaller test copy can establish the workflow before a long export consumes time and storage or becomes the only remaining version.
Read Apple’s documented export behavior
Apple’s export guide says QuickTime Player’s video exports are MOV files using H.264 or HEVC, rather than MP4 video exports. File, Export As offers appropriate output choices; larger-than-source resolutions are unavailable. Inspect the actual options for the opened movie.
Do not rename the resulting extension as a substitute for meeting the destination’s requirements. If another container is required, use an explicit supported conversion or remux workflow and verify its result. Preserve the original QuickTime export as a separate artifact until that task is checked.
Choose the offered format for the task
For applicable higher-resolution exports, Apple distinguishes smaller-file HEVC and greater-compatibility H.264 choices. Read the current menu and choose according to the real receiving route. A compatibility label is guidance, not proof that every legacy device supports every output combination.
Enter a new descriptive filename and a writable destination. Keep enough free space and allow the export to finish. A destination file appearing during processing is not sufficient evidence of a completed artifact. Retain the choice and source identity in the notes.
Inspect the finished output on its destination
Open the completed copy and check its beginning, middle and ending, required sound and actual media properties. Then test it through the intended receiving application or device. A file playing on the exporting Mac does not certify another playback environment.
The expected outcome is a deliberately chosen, complete output with an understood container and codec. It does not increase source detail, guarantee lossless conversion or bypass restrictions on protected recordings. Keep the original until the output and any later container conversion are independently verified.
Questions answered
Does H.264 mean the output container must be MP4?
No. Container and compression are different properties. Apple documents MOV video output for this export route.
Can changing .mov to .mp4 replace conversion?
No. Verify an actual supported output process and the resulting file on its destination.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.