You can simply delete the contents of the preview folder while LR is closed.
They will be recreated as needed.
Thank you for your prompt assistance! I need some clarification, please, is the preview the image I see in the Grid and Loupe views? If so and I delete the previews would I see greyed out 'images' for each photo in those files? Is there a tutorial on how to 'rebuild' the previews if needed in the future?
I have an additional question regarding deleting the contents of the preview folder.
When I open the .lrdata folder I see this:
So I right-clicked on Lightroom Catalog Previews.lrdata > Show Package Contents and I see this (expanded to show subfolders/files):
Exactly what should I delete? I am afraid to drag the entire .lrdata file to the trash. Aren't the previews.db and root-pixels.db files required as part of the LR software program? Sorry if these are stupid questions...
Delete the lrdata file as a whole you don't need to open it up. Lightroom will rebuild the previews on demand when needed automatically.
There is no danger of loosing anything as long as it is just the lrdata file you delete.
.lrdata is actually a folder with many subfolders. Just delete that .lrdata folder and LR will recreate it the next time you open LR.
Apologies for the tardy reply - many thanks for your help!
Thank you very much for your assistance.