The short answer
Yes. Rebuilt or re-downloaded automatically when needed.
What is it?
The “Previews.lrdata” package next to a Lightroom Classic catalog stores the thumbnails, standard and 1:1 previews shown in the Library module. On large catalogs it often reaches tens of GB, especially when 1:1 previews are kept.
Thumbnails and previews of the catalog. Lightroom rebuilds them as you browse.
What happens if you delete it?
Lightroom rebuilds previews as you browse, so the grid and loupe view are slower for a while. Photos, edits, keywords and collections live in the .lrcat catalog and are not affected.
How to remove it properly
Choose Library › Previews › Discard 1:1 Previews, and set Lightroom Classic › Catalog Settings › File Handling › Automatically Discard 1:1 Previews to a shorter period. Or quit Lightroom and move the Previews.lrdata package to the Trash.
Quit the app that uses it, then move it to the Trash. Empty the Trash when you’re sure.
Before you delete it
Remove only the Previews.lrdata package, never the .lrcat catalog file beside it.
How MoreRoom helps
MoreRoom recognises this item, shows its real size and when it was last used, and labels it “Safe to remove”. In the free version you can move it to the Trash in one click, with Undo; Pro collects every safe item at once.
Frequently asked questions
Is it safe to delete Lightroom Classic Previews.lrdata?
Yes. Rebuilt or re-downloaded automatically when needed. Lightroom rebuilds previews as you browse, so the grid and loupe view are slower for a while. Photos, edits, keywords and collections live in the .lrcat catalog and are not affected.
Will Lightroom Classic previews come back after I delete it?
Yes. Lightroom rebuilds previews as you browse, so the grid and loupe view are slower for a while. Photos, edits, keywords and collections live in the .lrcat catalog and are not affected.
How do I remove Lightroom Classic previews properly?
Choose Library › Previews › Discard 1:1 Previews, and set Lightroom Classic › Catalog Settings › File Handling › Automatically Discard 1:1 Previews to a shorter period. Or quit Lightroom and move the Previews.lrdata package to the Trash.