iMovie 10 stores all your Events (as well as your Projects and other related files) in the iMovie Library.
Right-click on it and choose Show Package Contents and you can see what's inside.
However, you shouldn't move, rename or otherwise change the contents of the iMovie Library in the Finder or you can really mess up iMovie.
If you want to delete Events or Projects, do it from within iMovie.
Thanks for the response, Matt. I did just find out I could show all the rejected clips in imovie. I selected all of them and deleted them. The imovie library file now is shrunk to 2.93GB. Still mysteriously large but a lot better than before. Any idea what those 2.93GB would represent and how I can get rid of that? Thanks.
A couple of thoughts....
When you convert your projects and events to iMovie 10 from iMovie 11, you have the option to keep your iMovie 11 Events and projects intact so you can continue to use iMovie 11.
If you took this option, it uses hard links so that both iMovie 11 and iMovie 10 can access the same clips but not take up double the space.
This has other implications:
1) If you delete your iMovie 10 event, it does not save you any space. You have to delete both the iMovie 10 and the iMovie 11 event to get back the space.
2) Hard links do not work when you copy to a new drive, so if you copy your iMovie 10 and your iMovie 11 events over to a new drive, now they will take up twice the space.
3) Therefore, if you are thinking of moving to a new drive, you should move the iMovie 11 events and projects over (from within iMovie 11). Then open iMovie 10 and convert the iMovie 11 stuff to iMovie 10, and it will use hard links and not take up double the space.
Hard links are also used in Time Machine so you can have the same file assigned to multiple dates without taking up more room. Also used in Final Cut Pro X extensively. For example, you can import your iMovie Events into FCP without doubling up space.
Here's my problem Re: Freeing up disk space, iMovie 10.0
I followed your advice and went to events and deleted everything in there.
I managed to gain 30GB so it's not that bad anymore.
Still, 20 GB for 1 video is a lot of space.
How can I make sure I can get rid of this?
Thanks in anticipation for your kind help.
All software latest version iMovie 10.1, El capitan's latest, MBP with 500GB of SSD disk and 8GB of memory,
What I have found is that iMovie 10 makes multiple copies of a video. One in the Library (maybe more, I haven't had time to fully research this), sometimes 2 in the Theater (not sure why 2) and who knows where else there are duplicates. And quite often duplicates of Event files. Not to mention pulling stills and video that you might temporarily attach to your movie, then leaving them there even after you delete them from the movie.
Seems Apple is trying to generate sales of external hard drives.
iMovie v9 was so straight forward on this subject it will be hard to deal with the new method of iMovie 10.
BTW, are all of you aware that iMovie v9 will NOT work with El Capitan?