Multiple Photos and iPhotos libraries

[Muflyer23]

A few years ago, I like many, transitioned from iPhoto to Photos. Concurrently, I also changed iMacs. I have a rather large photo collection (in excess of 33,000 images and videos) and somehow I have ended up with multiple iPhoto and Photos libraries. I would like to combine all these into one Photos library, but am not sure if there is any way to check various libraries to see if images are contained in one library, but not another. Individual comparison of images would simply be too laborious. Any help would be greatly appreciated. Also, if I open iPhoto libraries in Photos, I assume that has to be converted over and becomes a Photos library, correct? Doing so, seems to take a significant amount of time due to the quantity of images. Any way around this? Thanks.

 

[mpainesyd]

You might find Powerphotos useful
https://fatcatsoftware.com/powerphotos/

 

[Muflyer23]

Thanks for the suggestion.