How do I delete all photos that are not in any Album from iCloud Drive?

I'm using iCloud for backup. I use albums sporadically.

I like to delete all photos that are not already in any album.

Is there a simple way to do that or a tool or a web service I can use?


In macOS, Photos:

Choose File > New Smart Album.

Select from criteria Album, Is Not, Any.

Name and click OK.

Then select all then delete.

That way, you can delete all the photos that do not belong to any album.