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. If you prefer, you can store photos and videos outside the Photos library (for example, in a folder on your Mac or on an external drive) and still view them in Photos. Files stored outside your library are called referenced files.
Referenced files aren’t automatically uploaded and stored in iCloud, and they aren’t backed up along with the rest of your files when you back up your photo library — you must back them up manually. To avoid manually backing up referenced files, you can move or consolidate the files into your library.
Store imported files outside the Photos library
In the Photos app on your Mac, choose Photos > Preferences, then click General.
Deselect the “Copy items to the Photos library” tickbox.
Now, when you import photos or video, Photos leaves the files in their original location and accesses them as referenced files.
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.