Convert incompatible media in iMovie on Mac
As part of the transition from 32-bit to 64-bit technology in macOS, macOS Mojave 10.14 is the last version of macOS that includes support for video formats that rely on QuickTime 7. iMovie automatically detects media files that rely on QuickTime 7 and provides an option to convert the files to a format compatible with versions of macOS after macOS 10.14.
If you choose not to convert the files when you’re first alerted, you can have iMovie scan the library later and convert the incompatible files.
Important: To ensure future compatibility, make sure to convert the files before you upgrade to the next major version of macOS after macOS 10.14. After you upgrade, the option to convert the incompatible media will no longer be available.
Scan the current library and convert incompatible media
In the iMovie app on your Mac, choose File > Check Media for Compatibility.
If incompatible files are found in the library, a window appears listing them.
iMovie creates copies of the media files in the H.264 format. The original files are moved to an iMovie Incompatible Media folder, located in the same folder as the library. Your original media is not modified.
If incompatible files are missing or require additional software
When a library is scanned for incompatible media, iMovie may detect incompatible files that can’t yet be converted because they are missing, or because they require additional software (such as a codec). In that case, iMovie lists the files that are missing or require additional software.
In the iMovie app on your Mac, do one of the following:
If incompatible files are missing: Reimport the clips into the library.
For more information, see Import media into iMovie from your Mac, Import into iMovie on Mac from iPhone or iPad, Import into iMovie on Mac from file-based cameras, or Import into iMovie on Mac from tape-based cameras.
If incompatible files require additional software: Download and install the appropriate software.
For more information, see the documentation that came with the additional software.
To convert the files, follow the instructions in Scan the current library and convert incompatible media, above.
For information about media formats affected by the transition to 64-bit technology, as well as media formats compatible with versions of macOS after macOS 10.14, see the Apple Support article About incompatible media in iMovie for macOS.