How can I delete all photos not in an album?

make a new smart album (file menu ==> new smart album) for -- Album - is not - any

Open the album and select all and press command delete to move to the recently deleted album where they will be available for 30 days or until you delete them from it sooner

LN

You can collect all photos not in any album in a smart album:

• File > New Smart album
• Use the rule "Album > is not > Any".

This album will show all photos that are not in any album.

Select them with ⌘A and use the key combination ⌘⌫ (command-delete) to move them to the Recently Deleted album. Then delete the finally.

I would keep a backup copy of the library on an external drive. Just in case you regret deleting so many photos.

Sorry, the previous replies have been hidden for some reason.

Of course not - I have never done it and will never as I do not have all photos in albums - but yes it will do exactly what you want - it finds all photos not in any album and you delete them which is what you ask for

As to all versions of Photos , probably, it certainly works in Photos 3.0 and I am pretty sure it will work in your out of date version too - it is very simple and straight forward as long as that smart album criteria exists in your version

LN

See this article Use Photos on your Mac - Apple Support