iCloud Photos Library: Keep regular backups of your iCloud Photos!
It is easy to mistake iCloud Photos Library for a backup of our photos and to think, we are safe, when we turn on iCloud Photos on all devices. Apple promises: "Keep your photos safely stored and up to date on all of your devices". This perfectly true. I trust Apple to keep my photos safe and up to date.
Apple is storing them for us and syncing them across all devices. And if our device is lost or stolen, we can use iCloud Photos to restore the photos library to a replacement device.
We have essentially the one copy of our Photos Library in iCloud, mirrored and identical on all devices. That is fine as an off-site storage, but we need a backup as well to protect us from user errors. iCloud Photos does not provide an archival history to allow us to revert to a previous version of our Photos Library. If we mess our library up by deleting all photos or accidentally change the dates incorrectly, assign a wrong title, keyword, description to all photos, we cannot revert to the previous version. The changes in iCloud are immediate and sync to all devices.
When we enable iCloud Photos, our regular backup of our photos may be disabled by iCloud.
- on an iPhone or iPad the regular iCloud backup of the device will no longer include the photos. We have to save the photos regularly on a computer, once we start to use iCloud Photos.
- On a mac the Time Machine backup will include the Photos Library, but it will be incomplete, if iCloud Photos is enable with the "Optimise Mac Storage" option. The optimised originals will be missing, when we restore the library from a Time Machine backup. On macOS 10.14.6 or older the optimised versions will be completely removed and the albums will have gaps. On macOS 10.15 Catalina the optimised versions may remain as empty thumbnails.
The best backup of our iCloud Photos Library will be copies on an external volume, that have been copied, when the option "Optimise Storage" has not been enabled and all originals have been downloaded to the Mac. How to back up an optimised iCloud Photos Library - Apple Community
Another important reason for keeping a local backup is to have at least one copy of our photos and videos, that we can access, if the internet should not be working. We are better in control over the items we can access locally. We can check our backup if it is complete and working. This should be done, before we need to use it in an emergency and it is too late to recreate the backup.