I am the administrator of my computer, but iMovie wants "read and write permission"

This is what Gemini AI says and it usually sorts out my problems . . .

Upgrading macOS frequently resets system-level file ownership, access control lists (ACLs), or security attributes—especially when moving between major OS releases.

When a user sees a "permission denied" error opening an iMovie or Final Cut Pro library after a major system update, it is almost always caused by one of three things:

1. The OS Stripped Write Access on the Bundle

During the OS upgrade, the local user account UID/GID associations or extended attributes on the .imovielibrary bundle can get reset to Read Only.

The Fix:

1. Right-click the iMovie Library file in Finder and select Get Info (Cmd + I).
2. Expand the Sharing & Permissions section at the bottom.
3. Click the lock icon at the bottom right and authenticate.
4. Set the user account (or Everyone) to Read & Write.
5. Click the small gear / three-dots icon at the very bottom and select "Apply to enclosed items...". (This step is critical because iMovie libraries are folders disguised as single files; if sub-folders inside remain locked, the error persists).

2. Full Disk Access Permissions Were Reset

Major macOS updates routinely flush or revoke third-party app permissions under Privacy & Security, preventing iMovie from writing to external volumes or system folders.

The Fix:

1. Open System Settings > Privacy & Security.
2. Scroll down and click Full Disk Access.
3. Toggle the switch OFF and back ON for iMovie (or click + to add it if missing).
4. Restart iMovie.

3. External Drive Ownership Lock

If the library is stored on an external hard drive or SSD, macOS may have re-enabled strict ownership controls on that drive following the system update.

The Fix:

1. Click the external drive icon on the Desktop or Finder sidebar and press Cmd + I.
2. Expand Sharing & Permissions at the bottom.
3. Click the lock icon to unlock settings.
4. Check the box for "Ignore ownership on this volume".

Re: "I am the administrator of my computer, but iMovie wants "read and write permission"

This permission may have to do with allowing iMovie to import video and audio clips or files etc. for use in movie composing, editing, or creation, etc.

Eg: Read and write permission is generally for files, folders, or maybe external hard drives. Eg: Some files on your Mac may be protected (via copyright etc.) by the file's creators, or by digital rights management (ie "DRM": management of legal access) :

If necessary: See how to: Change permissions for files, folders or disks on Mac

and / or

What to do: If you don’t have permission to use files on a Mac disk - Apple Support

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© 2026 Resource: iMovie User Guide for Mac - Apple Support

More info., support, contact options etc: Website: iMovie - Official Apple Support