Aspect ratio of a Video in iMovie

The iMovie 10 screen is 16:9 in aspect ratio. That cannot be changed. The only ways to change a landscape video into a vertical video is to crop it vertical in the media browser (not timeline) view, or rotate it vertically from the the crop tool controls, leaving you with a sideways image..

So, by cropping, you can change the landscape vid from this . .

To this . . .

However, you would lose the cropped portions and you would still have the black bars on each side of the vertical display to make it fit the 16:9 iMovie screen.

-- Rich

You can trim out the black bars from the final exported. product with Quicktime player. Play it and do a screen recording with just the video part of the display outlined.

— Rich