Today’s Question: I have the opposite problem from the question about deleting previews [in Lightroom Classic]. I have many photos for which there is only a gray thumbnail, with no preview. They get built (slowly) when I browse each folder, but is there a way to simply build previews for all images in my catalog all at once?
Tim’s Quick Answer: Yes, you can generate standard previews for any photos that don’t already have them by selecting them all and then using the “Build Standard-Sized Previews” command.
More Detail: While standard previews in Lightroom Classic will be built automatically whenever you browse photos that don’t have the previews already, that can slow down the process of browsing your photos. It can therefore be helpful to build previews for all photos in the catalog if you are in a situation where not all photos have previews.
To get started, first make sure that all photos are currently available, such as by connecting any external hard drives that have photos stored on them. Then navigate to the All Photographs collection in the Catalog section of the left panel in the Library module. Next, on the Library Filter Bar above the grid view display, choose the “None” option so that no filter is set. Select all photos by choosing Edit > Select All from the menu.
With the photos selected, you can then go to the menu and choose Library > Previews > Build Standard-Sized Previews”. Lightroom Classic will then set about the task of building previews for any selected photos that don’t already have previews.
Note that this process can take considerable time, depending on how many photos you have in your catalog and the speed of the hard drive(s) on which your photos are stored. It is quite common for it to take several hours to generate all previews, or even a couple of days if you have a particularly large catalog.
