Merge Your Photo Libraries by Playing System Photos Library Musical Chairs
I started using iPhoto when it was first released for Mac a dozen years ago. It’s had a good run, but the new Photos app has been a welcome update. One of my favorite things about the new app is that it is fast…like really fast. It does all kinds of caching and memory management with iCloud to keep your library as nimble as possible. Back in the day large libraries would really slow down your machine to the point of being unusable. One of the strategies that I used with iPhoto on older machines was to break up my libraries. Every few years I would create a new library, which seemed to speed things up for me. I also kept different libraries on different machines and ended up just kind of collecting libraries over the years.
Long story short, I have several iPhoto libraries, but with the way things work now I really just want one big fat library for everything.
Currently there is no way to merge or import Photo libraries on your computer. However, you can upload everything from each library to iCloud by changing the System Photo Library on your computer.
Here is how to Designate a System Photo Library in Photos. If you want to give this a shot, just remember to keep a library designated until all photos have been uploaded before moving on to the next library. Rinse and repeat as needed. Your last library can remain your System Photo Library and all of your photos and videos will be in one place…finally.
You might have to upgrade your iCloud storage plan for this to work, but remember that you can always select the option to download a local copy of all images and video and then lower your plan later when everything is downloaded.