Cleaning up Smart Preview files

[Dan McKinney]

My Smart Previews folder is about 124 gigs, which seems to be to be unnecessarily huge. I do real estate photos, and I certainly don't need preview files for old listings. On a very irregular basis, I go through my hard drive and simply delete EVERYTHING in project folders except final edited JPGs, but I imagine LR still holds on to all the previews, right?

So, today I am using my file manager (XYplorer) to ferret out all DNG files in the Smart Previews.lrdata directory that are older than 90 days, and deleting them. Keeping the file structure the same, just deleting all the DNG files found within that are out of date.

Does that make sense?
 

[Dan McKinney]

I realize now that perhaps a better way to clean up old projects is to do it within LR itself so that the catalog would automatically stay on top of things! But should I assume that when I delete files from within LR that LR also deletes all preview files and any other catalog data associated with that deleted file?

[dj_paige]

You can delete Smart Previews on selected photos by selecting the photos you no longer want to have Smart Previews, and then Library->Previews->Discard Smart Previews.

[JohanElzenga]

Why do you have smart previews in the first place? Smart previews are not previews at all. That name is misleading. You don't need smart previews unless you want to be able to edit your images while the originals are offline (because they are on an external disk that is not mounted).

[Dan McKinney]

Good question! Why do I have Smart Previews? What is the difference between previews and smart previews? Are smart previews only for offline editing?

[Rob_Cullen]

" only for offline editing?"-  Only when the original camera files are 'offline'. eg. An external drive that is not connected.

https://mastering-lightroom.com/smart-previews-lightroom/

[JohanElzenga]

Good question! Why do I have Smart Previews? What is the difference between previews and smart previews? Are smart previews only for offline editing?

By @Dan McKinney

If you have a relatively slow computer, then you can also set in the preferences that Lightroom Classic should use smart previews for editing, even if the originals are online (because smart previews are smaller, this can speed up editing somewhat), but they have no other function. Like I said, the name is confusing. Smart previews aren't previews at all, they are small proxies for your original images. As you (apparently) did not know this, I would suggest you can delete them all.

[richardplondon · Accepted solution]

If you delete image files from disk without telling the Catalog: Lightroom not only retains previews and cached data of various sorts outside the Catalog (1:1 previews will eventually expire and be cleaned up) but also keeps hold of thumbnail images inside the Catalog, and of all your editing both global and local, plus other matters such as virtual copies and membership in Collections. These images will continue to show up inside the Catalog in searches of various kinds and when browsing the collections and folders panels. Each image (and the folder) will show a marker to indicate source file not currently findable by LrC.

But LrC cannot distinguish whether this image inside the Catalog is now permanently orphaned - or, just temporarily separated from its source e.g. while an external disk is unplugged. 

IMO a far better idea to clean up inside the Catalog and to have the source files deleted from disk as part of doing so. That of course loses all possibility of being able to come back and adjust any editing further.

So as a planned occasional task, one might decide to periodically archive off chunks of the Catalog along with the related source files, into other storage. That's if you want your main storage and your main Catalog kept relatively lean.

Perhaps highlight (say) everything from 2022, "Export as Catalog" to a completely separate (just) 2022 Catalog on an external disk, with copies of all the relevant source files alongside (tick selected images only, tick "include negatives") making that 2022 library selfcontained; then you can bulk remove all these same 2022 images out of your main Catalog - choosing Delete from Disk.

Deletion using the Catalog works file by file on disk, but does not delete the containing folders from disk. So this process will not incidentally sweep up any files that were not imported to LrC. For example: exported JPGs usually do not show in the Catalog, and so are none of its business.

[Dan McKinney]

Thanks Richard!!

[CS Chua]

There is no impact to the catalog if you delete smart previews. You could delete the entire smart preview folder where the catalog lives. Example if your catalog is name 2024 Lightroom-v13 there will be a folder by the name "2024 Lightroom-v13 Smart Previews.lrdata". 
You can safely delete that folder in its entirety. Lightroom will recreate this folder once you try to build smart previews for any photos. 

[CS Chua]

I have a method to keep smart previews to what I need. Typically you need smart preview if you want to be able to edit your photos on another device such as a tablet. What I do is only build smart previews for images I kinda of have them as WIP (work in progress or pending). My current is to marked all images that are synced to a particular color (you could use other method like keywords, ratings or even specific folder name etc.
Once you have establish how you want to identify images you allow to have smart preview .. use the filter library to filter them in or out. If filter out just select with ctrl-A on the filter ouput grid and select discard smart previews. On the other hand if you want smart previews, you build smart preview. To my understanding photos not in all sync photographs but in all photographs are not relevant so remove the smart previews from photos in that category. 
To discard smart previews