I formatted a new usb flash drive ExFAT, 1TB and copied my photos Library to it but when I try to open the library I first get an error (see pic) Library can't be opened. error 4302. I then select "open other" and select the same library again and then I get error PHPhotosErrorInvalidState. OS Catalina 10.15.1 (19B88)
MacBook Pro 15”, macOS 10.15
A Photos Library must not be stored on a volume with the format EX FAT. The file system format should be MacOS Extended (Journaled) or APFS. And the volume must not be used for Time Machine backups.
See: Move your Photos library to save space on your Mac - Apple Support
A flash drive is also not recommended, because of the possible data loss:
To prevent data loss, Apple doesn't recommend storing photo libraries on external storage devices like SD cards and USB flash drives, or drives that are shared on a network.
A Photos Library must not be stored on a volume with the format EX FAT. The file system format should be MacOS Extended (Journaled) or APFS. And the volume must not be used for Time Machine backups.
See: Move your Photos library to save space on your Mac - Apple Support
A flash drive is also not recommended, because of the possible data loss:
To prevent data loss, Apple doesn't recommend storing photo libraries on external storage devices like SD cards and USB flash drives, or drives that are shared on a network.
Here's your answer:
I formatted a new usb flash drive ExFAT,
The Photos Library needs to be on a volume formatted Mac OS Extended (Journaled) or APFS.
Thank you...I'll try that.
Does it matter which scheme I use when formatting (GUID, Master Boot, or Apple Partition)?
copied photos library to flash drive can't open