• Stop taking pictures.
• Using the Finder, navigate to the Photos Library folder. Photos Library is located in the Pictures folder of your home folder by default. Choose Go > Home from the Finder menu bar to access your home folder.
• Drag the Photos Library folder to an external storage device.
• Double-click Photos Library in its new place after the relocation is complete to open it.
• Designate this library as the System Photo Library if you use iCloud Photos.
• If you want to free up space on your Mac, move the original Photos Library from its original position (the Pictures folder of your home folder) to the Trash. After that, empty the trash can.

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