In iMovie 10.3.3, the chroma-key effect requires a well-lit, evenly-colored green or blue background. Overlay the clip in the timeline, then select the Chroma-Key button in the viewer window.
To properly access and download , you should use official Apple channels, as this version is a legacy release for macOS Catalina or Mojave (10.14.6 / 10.15.x). iMovie 10.3.3 is no longer the current version, but it remains available for older macOS systems that cannot run the latest iMovie (which requires macOS 11 or later).
In iMovie 10.3.3, the chroma-key effect requires a well-lit, evenly-colored green or blue background. Overlay the clip in the timeline, then select the Chroma-Key button in the viewer window.
To properly access and download , you should use official Apple channels, as this version is a legacy release for macOS Catalina or Mojave (10.14.6 / 10.15.x). iMovie 10.3.3 is no longer the current version, but it remains available for older macOS systems that cannot run the latest iMovie (which requires macOS 11 or later).