iCloud Photos is a great way to have all your images and videos across all your iCloud-linked devices. Apple lets you select an optimized option for storage, which ensures the full-resolution of your media is uploaded to iCloud and retained there (and accessible via icloud.com) while each end point, like an iPhone or Mac, has just a set of vastly reduced thumbnails. When you want to work with or view the full-sized photo or movie, double clicking or tapping retrieves it. You can have your cake (preserve storage on devices) and eat it too (have a huge Photos library).
The fly in that ointment is that with optimized image storage set on all your devices, you cannot make a local backup of all your media, as I explain in a 2017 column. I offered one full download strategy in 2018 for a reader who wanted to move from iCloud Photos to another service. Neither of these help with ongoing backups.
