Today’s Question: You referred to the cloud version of Lightroom not having the issues with a catalog the way Lightroom Classic does. But Lightroom does store an “lrlibrary” file on my computer. Isn’t that a catalog? Shouldn’t I be backing it up to protect my data?
Tim’s Quick Answer: The Lightroom Library file for the cloud-focused version of Lightroom is a local cache, not a catalog. What amounts to the catalog and your original photos for cloud-based storage are stored (and backed up) on Adobe’s servers, and there’s not really any need to back up the Lightroom Library file.
More Detail: Much has been made of the use of a catalog in Lightroom Classic, and understandably so. Because the information about your photos in the context of Lightroom Classic is stored in a central catalog file, it is important that all updates related to your photos be made within Lightroom Classic. If you were to rename or move photos or folders outside of Lightroom Classic, the catalog would no longer be connected properly to all your photos, and you could have a big mess on your hands very quickly.
With the cloud-focused version of the Lightroom desktop application there isn’t a central catalog. For photos stored in the cloud you can’t get to those photos outside of the Lightroom ecosystem, so there’s no way to end up with missing photos, since they are being managed in the cloud for you. For photos stored locally and managed with Lightroom, the software is behaving as a browser that does not employ a catalog, so you can make changes both inside and outside Lightroom without any problems.
The Lightroom Library file (which has a filename extension of “lrlibrary”) is simply a local cache. It enables you, for example, to browse and work with cloud-based photos even if you’re not online. The next time you do get online any updates will be synchronized back to the cloud. If you were to delete that file and then launch Lightroom it would simply be built for you again. The only way you would lose any data is if you deleted the Lightroom Library file after making changes while working offline in Lightroom. But assuming you’re connected to the internet while using Lightroom, the risk of losing any data due to a damaged or deleted library file is extremely small.