Learn what you can do if your photo library is over 1 TB.i Cloud Photo Library keeps a single library — your System Photo Library — up to date on all your devices.If you change your System Photo Library, the contents of this new library will be merged with the contents already in i Cloud.

And any changes or edits you make in Photos will not be reflected in i Photo or Aperture. Photos and videos from your System Photo Library will begin to upload to i Cloud in their full resolution and original format.

Photos will estimate the size of your collection and help you select a different i Cloud storage plan if needed.

i Cloud Photo Library will automatically manage the size of your library on each of your devices when you choose to optimize your storage in Photos i Cloud.

To migrate another photo library manually: Photos can use libraries from i Photo 8.0 or later and any version of Aperture.

If you’d like to migrate a library from i Photo 7 or earlier, use Apple’s free i Photo Library Upgrader tool to prepare your library first.

If you store your Photos library in a location that's part of a cloud service (for example, Dropbox, Box, or Google Drive), your library might be damaged by the syncing process. To see your photos on all your devices, you can use i Cloud Photo Library. i Photo — and Aperture, if you downloaded it — remains on your system in the Applications folder, and you can continue to use it.

If you open i Photo or Aperture after you upgrade to Photos, you’ll be asked if you want to open your library there or in Photos.

When you install OS X Yosemite v10.10.3 or later, Photos for OS X is part of the update.

In many cases, if you had a single i Photo library in your Pictures folder, your entire library — including your photos, videos, projects, albums, and so on — automatically appears in Photos the first time you open it.

If you have more than one photo library on your Mac, then Photos will ask which one you want to upgrade the first time you open it.

Photos allows you to open and work with libraries created in i Photo or Aperture.