A text box saying that "Photos App needs to quit: Photo library is being moved, is unavailable, or its data is corrupt" appeared on screen. None of those statements about the library should be true as far as we know. What will happen if we do quit? Is there any risk to the library?
iMac 21.5″, macOS 10.15
Are you in fact using macOS 10.15 Catalina, from 2019?
Have you used any "Cleaner" apps or "Virus Hunter" apps on your Mac?
We'd probably need to know more, but the first thing I think of is: where is your Photos Library located? Is it on an external drive? If so, how is your external drive formatted? To avoid damaging the Photos Library, an external drive must be formatted in either APFS format or Mac OS Extended (Journaled) format. The drive must be connected directly to the Mac by cable, not networked, clouded, NASed, etc. Additionally, the drive can not have had Time Machine on it since it was formatted. There have been so many problems with using incompatible drives that the newest macOSs won't even allow a Library on a non-Mac formatted drive to open, since there is a chance of damaging the Photos database. See this:
https://support.apple.com/en-us/108345
If this drive is in a an incompatible format, stop running Photos with it immediately! A Photos Library can sit on an incompatible drive, but running it may corrupt the database.
You can locate Photos Library by closing Photos and then option-clicking on the Photos icon. This brings up the Library Chooser:
where you can see the list of Libraries that Photos knows about, along with the path to them. Most people have only one Library, but many people have several.
Check these things out, and the we can explore further…
Are you in fact using macOS 10.15 Catalina, from 2019?
Have you used any "Cleaner" apps or "Virus Hunter" apps on your Mac?
We'd probably need to know more, but the first thing I think of is: where is your Photos Library located? Is it on an external drive? If so, how is your external drive formatted? To avoid damaging the Photos Library, an external drive must be formatted in either APFS format or Mac OS Extended (Journaled) format. The drive must be connected directly to the Mac by cable, not networked, clouded, NASed, etc. Additionally, the drive can not have had Time Machine on it since it was formatted. There have been so many problems with using incompatible drives that the newest macOSs won't even allow a Library on a non-Mac formatted drive to open, since there is a chance of damaging the Photos database. See this:
https://support.apple.com/en-us/108345
If this drive is in a an incompatible format, stop running Photos with it immediately! A Photos Library can sit on an incompatible drive, but running it may corrupt the database.
You can locate Photos Library by closing Photos and then option-clicking on the Photos icon. This brings up the Library Chooser:
where you can see the list of Libraries that Photos knows about, along with the path to them. Most people have only one Library, but many people have several.
Check these things out, and the we can explore further…
BackyardBlessing wrote: Photos library is on iMac Hard drive, which is actually a 1 TB solid state drive that was installed at an authorized service shop around 5 years ago.
That's good. Check the format by selecting the drive and using Get Info with ⌘-i.
Did you ensure that the Library is the System Library?
More than likely these things are OK, but we need to be sure.
The function of the Norton stuff is largely unnecessary, and it is way more likely to cause trouble than to prevent it. You should do as Yer_Man suggested and uninstall it.
When all that is done, you should re-boot the Mac and see how things are going. If there are still problems, the best thing to do next is to try a Safe Restart--This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this:
Start up your Mac in safe mode - Apple Support
I have to write the instructions down (or print them,) because, ironically, while restarting I can't go back to the computer to see exactly which buttons to push.
Let us know how it goes…
Get rid of the Norton products using their uninstall instructions and try again.
Do you have a back up of the Library?
Have you tried launching your library with the Option+Command keys held down to restore/repair the library?
When you start looking for a new Mac consider the following: a 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($1084 US) with a 32" LG 4k monitor ($331 US) from Amazon.com) is $1415 US which is $541 US less than a similarly configured new 24" iMac ($1956 US) re 07/2025. Keep your keyboard and mouse from your current Mac for use with the Mini.
I got the above Mini with a 32" LG 4K monitor w/speakers for only $60 US more than the 27" (didn't know the Mini had a speaker). There are many monitors available in 27" size for $100 US to $500 US depending on what features you want. The prices are before tariffs.
Just some food for thought.
"...except Norton"
Which Norton app? That brand have a long and storied history of hosing Mac installations.
Photos library is on iMac Hard drive, which is actually a 1 TB solid state drive that was installed at an authorized service shop around 5 years ago. Have had no other issues with it. Operating system is Catalina 10.15.7. iMac is late 2012. Will be shopping for new machine very soon, but don't want to mess up library of around 100K photos. Library is also on iCloud. Also, have not used any "Cleaner" or "Virus hunter" - like Apps except Norton.
Norton 360 Antivirus, Safeweb, secure VPN
Photos App: 'Photos App needs to quit' error
