A prompt will appear stating the current version is incompatible but offering to download the for your OS. 2. Trusted Third-Party Repositories
If you have previously "purchased" (even for free) iMovie on your Apple ID, you can download the last compatible version directly from the Mac App Store .
If the App Store method fails (e.g., if you never "bought" iMovie on your current account), some software archives host the original installer:
Improved reliability when exporting projects with specific language and region preferences.
Avoid downloading DMG files from unknown or unverified sites to prevent malware. Always check the digital signature of the installer if possible.