How to Convert a Video on Mac

The fastest way to convert a video on Mac depends on what's inside the file. For an H.264 MOV, Apple's own documented method is simply to rename the extension. For anything else, the conversion runs through iMovie. Here's how to tell which one you have.

The extension is a label; the codec is the content

.mov and .mp4 are containers. Boxes that hold the streams. H.264 and HEVC are the codecs, the actual compression of the picture inside the box. They're independent, which is why the extension on a file tells you much less than people assume.

When a video refuses to play somewhere, the codec is usually the reason. A machine that can't decode HEVC won't play HEVC whatever the file is called; a machine that can decode H.264 will generally play it out of either container. Renaming a file changes the label on the box, not the contents, so it only helps in the specific case where the contents were already acceptable and the label wasn't.

That case is common enough that Apple documents it.

Convert a video on Mac by renaming, when the codec allows it

For a MOV file that uses the H.264 codec, Apple's instruction is direct: Control-click the file, choose Rename, select the mov extension, type mp4 after the period, and press Return. That's the whole procedure. Nothing is re-encoded, so nothing is degraded and it's effectively instant.

It's worth being clear about what this is not. It isn't a universal trick for any file ending in .mov, and Apple scopes it to H.264 for exactly that reason.

One more thing that surprises people: QuickTime Player doesn't export movies as MP4. Its File > Export As menu produces QuickTime movies at various sizes, which is a different thing. If you've been hunting that menu for an MP4 option, it was never there.

The route that works whatever the codec

For files the rename won't cover, Apple's documented path is iMovie. In Projects view, click Create New and choose Movie. Click Import at the top of the window, find your file, select it, and click Import Selected. Then click Share, choose Export File, click Next, pick a location and click Save.

This one does re-encode, so it takes real time on a long clip and costs a small amount of quality, but it works regardless of what the source was, which the rename doesn't.

Nothing to choose, so nothing to choose wrongly

Montaj sidesteps the question by only producing one thing: an .mp4 in HEVC, every time, from every project. There's no format menu to choose wrongly and no MOV to discover later, because the container and the codec were decided once rather than per export.

It runs on your device, with nothing uploaded. If you need H.264 specifically for an older machine, convert a video on Mac through iMovie as above. That's the case where having the choice matters more than having it made for you.