Today’s Question: I deleted the Previews file associated with my Lightroom Classic catalog when I was urgently out of hard drive space. Now that I’ve cleared up plenty of space, is there a way to rebuild previews again for all photos? Right now it is really slow to browse images when I select a folder.
Tim’s Quick Answer: Yes, you can select all photos in the All Photographs collection and build previews for all of them. This will take considerable time, but it will then speed up browsing once the previews have been generated.
More Detail: The file that contains the standard previews for your Lightroom Classic catalog can get quite large, making it a prime choice for deletion if you need to free up considerable hard drive space quickly. For example, the previews file for my catalog is over 200GB in size.
The standard previews generated by Lightroom Classic help improve the speed with which you can browse through your photos. If you delete the previews file then browsing can become quite slow because Lightroom Classic needs to generate previews on the fly as you browse various folders of photos.
Therefore, if you’re able to free up adequate storage space on the drive that contains your Lightroom Classic catalog, it can be very helpful to build previews for all photos again. This is true whether you had deleted the previews file or you neglected to have standard previews built during import, for example.
To build previews for all photos, first select the “All Photographs” collection in the Catalog section of the left panel in the Library module. Then be sure to choose “None” from the Library Filter bar above the grid view to ensure all photos are displayed. If the Library Filter bar doesn’t appear above the grid view you can choose View > Show Filter Bar from the menu.
Next, choose Edit > Select All from the menu to select all photos. If your photos are stored on one or more external hard drives, be sure those are connected to the computer so the photos are available. Then choose Library > Previews > Build Standard-Sized Previews from the menu to start building the previews.
The process of building all previews can take considerable time, from hours to days depending on how many images you have and the hardware configuration for your computer and storage. But once the previews are built, you’ll be able to browse your photos much more quickly again.
