Lightroom Classic's Preview file does not shrink in size when discarding Standard and 1:1 Previews

Forum|Forum|4 months ago
January 1, 2026
2 replies
1290 views

LrC 15.1 on macOS Tahoe 26.2

Catalog contains around 98.000 RAW files

Lightroom Catalog Previews.lrdata is over 300 GB large (containing all Standard Previews of all RAW files, but almost no 1:1 previews)
Trying to reduce the file size from 300 GB to less than 200 GB by discarding the Standard Previews *and* the 1:1 Previews from almost half of my catalog's RAW files (the oldest ones) by using the command in the Library menu item (Library > Previews > Discard Standard and 1:1 Previews...) does not change the Lightroom Catalog Previews.lrdata size in any way. The file is still over 300 GB.
Restarting LrC nor Restarting the iMac helps.
The command seems to run fine, showing the progress bar in the upper left corner of the UI window of LrC, but fails to shrink the file size of the previews file. Thus no previews were discarded and the command does not function as it should.

macOS

J

Jeff_Warner

Known Participant

I'll trade you. Mine has been at 1TB on a 2TB drive for years. I last trashed the file and started over in 2019, and within weeks it was right back to 1.1 TB, and never changes, up or down. It's infuriating.

J

Jao vdL

Community Expert

It takes a long time to actually remove the previews you discarded in my experience. I think it only marks the previews you discarded as removed and slowly cleans up in the background when it determines you actually wanted to get rid of them - i.e. you do not actually zoom in again to 1:1 to necessitate a 1:1 preview.

The Keeper of the GardenAuthor

Inspiring

This is far from a correct answer, as it was marked as such!

Please re-read carefully my detailed, logical, and precise post. This has nothing to do with 1:1 previews but everything with *STANDARD* previews. I tried to "discard" the Standard Previews of photos (RAW files) that had absolutely no 1:1 previews, as I had not viewed/edited these old photos for years, and all of my 1:1 previews are discarded automatically by LrC after one week...
So, the bug is there and has nothing to do with the "solution" you offer.
Anyway, discarding a file should always be instantaneous. We're talking about computers and software, not about something you throw in the cellar and get rid of a year or two later.

J

Jao vdL

Community Expert

The same thing is true for standard previews - sorry if I did not make that clear. The culling from the preview database for any size preview is not instantaneous. It is how they implemented it. I agree it would be preferable and logical if it were instantaneous but it clearly isn't. I have seen this on my catalogs where it will slowly decrease the preview database after you selected "discard standard and 1:1 previews". I think it won't actually discard standard previews in that case if you have recently touched or viewed the image - don't know what the time constant for that is. Also note that it will recreate standard previews in the background over time regardless if you discarded them so discarding standard previews usually has little effect. Only when you set the standard preview size to something smaller will you end up with a smaller preview database after discarding them since the recreated previews will be smaller size.

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