Where apps hide your files

Where Lightroom hides its gigabytes

Updated 2026-08-08 · 4 min read

Photographers watch their photo drive carefully and their catalog folder not at all. That folder quietly accumulates previews of every photo you have ever imported, at sizes that eventually rival the photos.

The three growers

Next to every Lightroom Classic catalog:

• <catalog> Previews.lrdata — rendered previews of your photos. Grows with the

library, easily into tens of gigabytes.

• <catalog> Smart Previews.lrdata — small raw copies that allow editing with

originals offline. Only exists if you built them.

• Camera Raw cache — under ~/Library/Caches, default 5 GB but configurable, and

often raised long ago and forgotten.

Trim previews safely

Previews regenerate on demand. In Lightroom → Settings → File Handling, set 1:1 previews to discard after 30 days. For an immediate reclaim: quit Lightroom and delete the Previews.lrdata package next to the catalog — the catalog itself, the .lrcat file, is untouched and Lightroom rebuilds previews as you browse.

Do not delete Smart Previews casually if you edit with originals on a disconnected drive; that is precisely what they are for.

Find every catalog you own

Old catalogs from machine migrations and one-off projects each carry their own preview packages. Search for .lrcat across every drive — and note that Spotlight cannot see the ones on unplugged archive disks. This is a case where an index that persists across drives, Everywhere's included, turns an afternoon of plugging things in into one query.

The photos themselves

None of the above touches originals. Moving those to an external drive is a separate exercise, and Lightroom tolerates it well: move the folder in Finder, then point the folder at its new location inside Lightroom's Folders panel.

Common questions

Can I delete Lightroom's Previews.lrdata?

Yes, with Lightroom quit. Previews are rebuilt as you browse. The catalog file itself must never be deleted.

What is the difference between previews and Smart Previews?

Previews are for display. Smart Previews are editable small raws that let you develop photos while the original drive is offline.