Moving iMovie (10) libraries to external hard drive I have a friend who have a 13&quot; macbook pro from 2014.
The OS is Yosemite 10.10.15.

My friend would like to upgrade her OS to either High Sierra or Mojave or even maybe Catalina or Big Sur, however she has a pretty big iMovie library and thus she can't upgrade because the iMovie library takes too much disk space.
Also she would like to move her iMovie library to an external hard drive, which would also solve the disk space problem.
Obviously, even if the iMovie library is on her external hard drive she'd still like to be able to work on it with her macbook.

The issue I have is that I found plenty of ways to do this with iMovie 11+ but with iMovie 10 the tutorials I found sometimes specify some particular manipulations and sometimes not, so I am not very confident about the manipulation I should do on her macbook.

Could anyone point me to a safe tutorial to do this ? Or explain me step by step how should I do this ?
Also I guess that after upgrading her mac OS she will want to upgrade her iMovie software, is there any compatibily issue I should be aware of ?

I am pretty tech savy, but I don't know a lot about mac OS and even less about iMovie...
As a side note, I made her format her external hard drive in extended mac OS, and I did a partition for time machine and an other partition for her iMovie stuff.
You can just move it, anywhere, then tell iMove to find it again on next launch.
As the library presents itself to the Mac as s single file (even though technically it's a 'special' folder) then dragging to a new location, or Cmd/dragging to move rather than copy, is all that's required.
You can force a new library to be requested if you hold the Opt key immediately after double-clicking to launch. iMovie is capable of switching between multiple libraries this way, if required.

If it doesn't show in that list (which it won't if it's moved) then use Locate… &amp; navigate to it.
It will continue after that to use the new location until told otherwise.
Older versions of iMovie used to keep the original footage separately - so if you see separate folders named iMovie Events, Exports, Original, Projects etc, then move those too. If any of these folders contains a file called UpdatedToiMovie10 then you should be OK without them, but better to check inside iMovie itself before permanently discarding.