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TomHackettPhotography
Known Participant
August 13, 2025
Answered

Previews for images on external devices have disappeared from Lightroom Classic

  • August 13, 2025
  • 1 reply
  • 515 views

My workflow for several years has included migrating images to external devices (USB connected hard drives) when I need space on my hard drive.  I do this by creating a folder on the external hard drive, selecting the images to migrate and then dragging them to the new folder in Lightroom.  This has worked very well for several years.

Yesterday I was surprised to see that the previews for the images with the '!' symbol (the ones that had been migrated off of the hard drive) were missing.  The metadata was still there and appeared accurate, but instead of a picture, I saw only a gray box.

In most cases, I am able to get the preview back by attaching the external device and clicking on the '!' symbol to find the image.  But I have around 20 thousand images in my catalog, and there are hundreds of  missing previews.  I can use ratings, labels and sometimes text to filter the images somewhat, but getting back the image previews I want for a particular project is still time consuming.  

I had this problem some time ago--different computer, different catalog--when I used Library > Previews > Discard. . . on a number of older images.  That was a mistake I hope never to make again, but I can't think what I might have done to cause a prolem this time.  Any suggestions on how to get my previews back would be appreciated.  I backup my catalog daily, if that helps.

Computer:  MacBook Pro 16 inch, 2023 with Apple M2 Pro chip

Operating system:  macOS Sequoia 15.6

Lightroom Classic 14.4 (Any chance upgrading to 14.5 will address this?)

 

    Correct answer JohanElzenga

    To answer the last question first: no, restoring the catalog from a backup would be useless. Previews are not stored in the catalog file, but in 'catalogname previews.lrdata'. That is the 'previews cache' we are talking about and that is not backed up. The reason you see missing previews is because the preview format has changed fairly recently (I don't remember the exact version number but it was sometime in the last 12 months). That means older previews are obsolete and need to be replaced by previews in the new format, but as long as the originals are offline or missing because you moved them outside of Lightroom, Lightroom can't do that. To fix missing images in batch, do not click on the exclamation mark but try to reconnect them by folder: https://www.lightroomqueen.com/lightroom-photos-missing-fix/

     

    1 reply

    davescm
    Community Expert
    davescmCommunity Expert
    Community Expert
    August 13, 2025

    Hi 

    In Lightroom's Preferences > Performance Catalog Settings > Go to Catalogue Settings  > Previews   do you have 'Limit Preview Cache Size' set?

    Some more reading here  : https://helpx.adobe.com/uk/lightroom-classic/kb/optimize-performance-lightroom.html

    I'll move your thread to the Lightroom forum.

    Dave

     

     

    https://helpx.adobe.com/uk/lightroom-classic/help/create-catalogs.html?trackingid=TY6XKS59&mv=in-product#customize-catalog-settings

      T
      TomHackettPhotographyAuthor
      Known Participant
      August 14, 2025

      Thanks for looking at this , Dave.  I have not set the 'Limit Preview Cache Size.'  I'm attaching a screenshot of my previews settings.  

      I'm a little confused about terminology here.  Is the Preview Cache in RAM or in a file?  I have two files that look like they might be relevant.  [Catalog name] Previews.lrdata (currently 23.71 GB) and [Catalog name] Smart Previews.lrdata (599.9 MB).  Would it be possible to recover at least some of the missing thumbnails by restoring a backup of the catalog?

      JohanElzenga
      Community Expert
      JohanElzengaCommunity ExpertCorrect answer
      Community Expert
      August 14, 2025

      To answer the last question first: no, restoring the catalog from a backup would be useless. Previews are not stored in the catalog file, but in 'catalogname previews.lrdata'. That is the 'previews cache' we are talking about and that is not backed up. The reason you see missing previews is because the preview format has changed fairly recently (I don't remember the exact version number but it was sometime in the last 12 months). That means older previews are obsolete and need to be replaced by previews in the new format, but as long as the originals are offline or missing because you moved them outside of Lightroom, Lightroom can't do that. To fix missing images in batch, do not click on the exclamation mark but try to reconnect them by folder: https://www.lightroomqueen.com/lightroom-photos-missing-fix/

       

      -- Johan W. Elzenga
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