Since iDVD is discontinued by Apple for years, there's no free built-in alternative in Mac to burn iMovie file to DVD, not to mention the latter Blu-ray. But to create Blu-ray disc from iMovie video on your Mac, you'd need third party applications.

If your video files exported from iMovie play correctly in QuickTime player, you can just drag it into the iDVD of iLife suite and it can burn to DVD on your Mac.

For playback iMovie project on a designated Blu-ray/DVD player, you need a disc burning app that creates the video-disc. IMovie itself does not support any creating of Blu-ray and DVD. That is what we're going to talk about - how to burn an iMovie project to a Blu-ray or DVD on Mac. If you are a fan of physical media, you may want to create Blu-ray or DVD disc to store and share the video project you done in iMovie. IMovie is a video editing software application included in Macs that lets you process common and high-definition video from AVCHD camcorders and H.264-compressed video from MPEG-4 or QuickTime Movie files, and export to create beautiful movies and Hollywood‑style trailers. How to Burn iMovie Project to Blu-ray/DVD

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