Migration
A database, not a folder of images
A Lightroom Classic catalog is an .lrcat file: a SQLite database that contains no photographs. It contains pointers to your files, plus everything you have decided about them.
That distinction carries weight. Losing your images is a disaster. Losing the .lrcat while keeping the images is a different disaster, often underestimated: the files are there, and years of culling, keywording, and settings are gone.
What the .lrcat file stores
- File locations across your volumes, with their folder tree.
- Curation: 0-to-5 star ratings, picks and rejects, colour labels.
- Keywords and their hierarchy.
- Collections, including nested ones, with their manual ordering.
- Virtual copies and stacks.
- Develop history and settings, step by step.
- Entered metadata: captions, titles, rights, locations.
Alongside it, Lightroom maintains previews in a separate .lrdata folder, which is not the catalog and can be regenerated.
Three things worth knowing
The catalog is a single point of failure. Corrupt the database, and everything not written into the files or their sidecars is gone. Hence the value of enabling automatic XMP metadata writing: it’s a second copy of your descriptions.
It locks you in by nature. The format is proprietary in its internal organisation, even though SQLite is open. Reading an .lrcat without Lightroom means understanding its schema, which changes between versions.
It can be read safely. A catalog can be opened read-only by a third-party tool without being modified. That’s what makes a migration possible without putting the existing setup at risk.
What carries over, and what has limits
Structure and curation carry over well: ratings, picks, keywords, nested collections, ordering, virtual copies, stacks. Develop settings, however, are the interpretation of one specific rendering engine. No other application reproduces them identically; they should be archived verbatim as documentation, not as replayable instructions.
In practice
- Back up the
.lrcatseparately from your images — they are two distinct losses. - Enable automatic XMP metadata writing.
- Don’t count
.lrdatapreviews in your backups: they regenerate. - Before migrating, copy the catalog and work on the copy.
Obscura Flow opens .lrcat catalogs read-only, never modifying the original, carries over curation, keywords, collections, and versions, and archives develop history verbatim rather than claiming to replay it.