When you’re finished creating a project, you can finalize it. With this process, iMovie prepares (renders) your movie in all of the possible sizes—mobile, medium, large, HD 720p, and HD 1080p—that your project’s media supports. (Sometimes, the original project media isn’t large enough to render in the largest sizes.) You don’t see the finalized files in iMovie; rather, iMovie uses the files when you share a project to MobileMe or a social media website such as Facebook or YouTube. When you finalize a project in advance, the process of sharing a movie takes less time.
Finalizing a project also improves full-screen playback because iMovie also uses the rendered files when you play a project in full-screen mode.
To learn about sharing your movie projects, go to the “Share your video project” section of iMovie Help.
To finalize a project:
Click to select a project in the Project Library, or open a project so that it’s showing in the Project browser.
You should finalize only projects you consider to be complete because if you make further changes to a movie you’ve finalized, iMovie discards the finalized versions.
Choose File > Finalize Project.
The File menu appears in a light gray bar across the top of your computer screen.
Depending on the size of your project, it can take a while to render all of the sizes. You might want to finalize your project when you’ll be away from your computer.
The process is complete when the finalizing dialog disappears.