You can resize a video project in iMovie by exporting the clip using expert settings. The Size option in the Export Settings menu enables you to change all of the frames in the clip at once to a designated size. The Size option is not supported by all video file formats. If supported, the Settings button appears in the Export pop-up window when configuring the expert settings for your file. You can also reduce the file size of a clip by exporting and then re-importing the file.

Step 1

Open your video project in iMovie, then click the “Share” option in the top menu bar to open the Share menu.

Step 2

Type a title for the exported clip in the Save As dialog box.

Step 3

Click the blue arrow icon to navigate to the location where the exported file will be saved. Select the destination folder.

Step 4

Click the “File Format” box, and then click the desired export file format.

Step 5

Click the “Settings” option, then click the Key Frame field. Increase the key frame rate to reduce the file size of the exported clip. Increasing the key frame rate, however, will reduce the quality of the exported file. You can also click the “Compression Type” drop-down box, then select different compression types to further reduce file size. Options for Compression Type depend on the selected export format.

Step 6

Click the “Size” button. If you opted for QuickTime as your export format, the Size option is available to resize all frames of your video project at once. A pop-up menu displays the current screen size of the video frame along with additional size options. The available choices are “Mobile,” “Medium,” “Large,” “HD 720p” and “HD 1080p.” Click the desired screen size from the pop-up menu.

Step 7

Click “Save” to save the settings and export the resized video.