Where are the photos I imported into Photos on my Mac?
When you first use Photos, you create a new library. New photos and items that you add to Photos are stored in the Photos library. This library automatically becomes your System Photo Library, which Photos accesses each time you open the app. Only your System Photo Library can receive photos transferred by iCloud Photos. By default, the System Photo Library is located in the Pictures folder on your Mac.
You can also create additional photo libraries on your Mac and on other storage devices. You should always use the Photos app to access the photos in a Photos library.
WARNING: To avoid accidentally deleting or corrupting a Photos library, do not alter the contents of a library in the Finder. If you want to copy, move, or transfer files, first export them from the Photos library; do not manually access or change the library in the Finder.
If you import items from a storage device or another folder on your Mac, you can have Photos leave the items in their original locations so they don’t take up extra space on your Mac.
Although storing files outside your Photos library is a great way to save space on your Mac, be aware that:
If you use iCloud Photos, photos and videos that are outside the Photos library aren’t stored in iCloud and won’t be accessible to any other Mac or device that uses iCloud Photos.
If you disconnect the device where the files are located, or move or rename the files in the Finder, Photos won’t be able to locate them.
Tip: If you use iCloud Photos, another good way to save space is to turn on Optimize Mac Storage in the iCloud pane of Photos settings. iCloud Photos then places smaller photo files on your Mac as needed, but all the full-size photos and videos are still accessible to your Mac from iCloud.