Can I use an external hard drive to store my Photos library?

Hi - You can completely move the library to external storage with the disadvantage that you must have the external storage connected whenever you want to use photos. (in fact you should have it connected whenever you log in) You can then still use the photos app to view, manage and edit your photos.

The external storage must be formatted APFS or MacOS extended (journaled), and not be (or have been) used for time machine. It must have the 'ignore ownership" checkbox ticked. It should not be on a memory stick, SD or similar. It stands to reason that if you want any sort of reasonable performance it should be a fast drive with a fast connection.

See

https://support.apple.com/en-gb/HT201517

Yes, if it's formatted properly and backed up to another location. Drag the library there, launch Photos with the Option key held down, click on Other Library, and choose it.

(189348)