HOW TO DELETE IMOVIE FILES FROM THE HARD DRIVE

Open a project and click on the project's title under Project Media at the top of the sidebar. The clips associated with that project will appear in the media browser pane. Select a clip in the pane and do File/Reveal in Finder. A folder will pop up entitled Original Media. Displayed in the folder will be the clips associated with the project. The clip that you had selected will be highlighted. You can delete the clips from there and they will be permanently removed from the iMovie library and free up storage space.

You can also delete an entire Event (the Event itself, not just the media in it) and that will also serve permanently to delete the files from the iMovie library and from all projects that might be referring to the deleted clips. (See the help link below for instructions.)

WARNING: Deleting a clip from the Original Media folder or deleting an Event will remove it from all projects that may be referring to it, thus disabling those projects. Further, unless you have stored duplicates of your media outside of iMovie, you will permanently lose your source files.

Here is a link to Apple's help menu that explains how to delete media from iMovie:

https://help.apple.com/imovie/mac/10.1/#/mov74d7d370c

Rather than deleting media from the iMovie library a better way is to store your library on an external drive that is formatted Mac OS Extended (Journaled) or APFS. iMovie will refer to the library on the external drive.

Also, to free up more storage space you can go to iMovie preferences (iMovie > Preferences) and delete the Render files from the preferences box that appears.

-- Rich

Adding to my previous post, an iMovie project contains no original media, but rather only tiny sized reference thumbnails for editing purposes. When you delete from an iMovie project or from within an Event you are

only deleting a reference thumbnail and so little or no space is freed up. The thumbnails refer to the original media that is contained in the Original Media folder, that is a Finder folder. So, when you delete from the Original Media folder you are deleting from the Finder and that's way more space is freed up. But then iMovie no longer has the media to refer to, and therefore all projects that may have referred to the media are disabled.

-- Rich

Adding to my previous post, an iMovie project contains no original media, but rather only tiny sized reference thumbnails for editing purposes. When you delete from an iMovie project or from within an Event you are

only deleting a reference thumbnail and so little or no space is freed up. The thumbnails refer to the original media that is contained in the Original Media folder, that is a Finder folder. So, when you delete from the Original Media folder you are deleting from the Finder and that's why more space is freed up. But then iMovie no longer has the media to refer to, and therefore all projects that may have referred to the media are disabled.

-- Rich