Here's how you can do it in Safari: go to Preferences -> Advanced to enable the “Show Develop menu in menu bar” option. Depending on which browser you're using, the steps might be different.

Remove junk files like caches: Go to the folder ~/Library/Caches /Library/Caches (without the ~), and enter each folder and delete the files inside.

Go to the Application folder and uninstall huge applications that you don't need any more.

Empty trash to remove files permanently.

Below are methods you can try to clean up space for iMovie. You're able to manually remove files with big size, or use cleaning software like IObit MacBooster which can help you find 20 types of junk files so that you can delete them safely to free up disk space. If your Mac is running out of disk space, it's time to perform a complete scan and clean on your Mac's hard drive disk.

IMovie Not Enough Disk Space Solution 1: Remove Files from Mac > iMovie Not Enough Disk Space Fix 3: How to Clean Up iMovie Library > iMovie Not Enough Disk Space Fix 2: Re-download and Install iMovie > iMovie Not Enough Disk Space Fix 1: Delete Files to Release Storage Space You'll see how to clean up iMovie library in Fix 3. You'll see the file size of iMovie Library.

To view the file size of iMovie Library, go to your home folder and enter the folder Movies.

If there is sufficient disk space, this is not a space issue, try Fix 2. 25GB is recommended, and the more, the better.

To confirm the storage status of your Mac, go to the Finder menu and click on Apple Logo/About this Mac/Storage and make sure that you have at least 5 GB free space.

Here is how to check the available storage and the file size of iMovie Library. So first go to ensure this is really a disk space related problem when you see the error message prompted as above. The iMovie library file could be tremendous if you go to check its size. The iMovie Not Enough Disk Space issue might not happen on new macOS desktops or MacBooks, but it does appear on many machines if they have been using iMovie frequently, when you try to import media to iMovie for editing.

Problem Fixed: iMovie Not Enough Disk Space Error

Mac says disk is full