Change where your files are stored in Photos on Mac
When you import photos and videos into Photos, they’re copied to the Photos library in the Pictures folder. To save storage space, you can store photos and videos outside the Photos library (for example, on an external drive) and still view them in Photos. Files stored outside your library are called referenced files.
Store imported files outside the Photos library
In the Photos app on your Mac, choose Photos > Settings, then click General.
Deselect the “Copy items to the Photos library” checkbox.
Now, when you import photos or video, Photos leaves the files in their original location and accesses them as referenced files.
If you store files outside the Photos library, keep in mind 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.
Referenced files aren’t automatically backed up along with the rest of your files when you back up your photo library—you must back them up manually.
Find a referenced file in the Finder
In the Photos app on your Mac, select a referenced file.
Choose File > Show Referenced File in Finder.
Copy referenced files into a Photos library
You can copy referenced files into your photo library so they’re easier to back up and are automatically stored in iCloud if iCloud Photos is turned on.
In the Photos app on your Mac, select the files that you want to copy into the photo library.
Choose File > Consolidate.