Storage of thumbnail/previews

Hi together,

I am using current Nextcloud release. I am wondering where Nextcloud 12 stores the thumbnails? Coming from NC 11 I think I’ve seen a folder called files_thumbnails or something like that. With Nextcloud 12 there is no such folder. I am asking because something went wrong during thumbnail generation and now I got a black image. And I can’t recreate the thumbnails. Any help please?


Since NC12 all apps, including gallery, use a new core preview system, where the previews are stored in data/appdata_<instanceid>/preview.

The old data/<user>/thumbnails folders are not used anymore and can be removed by the way. You can use occ preview:delete_old to let this done, in case you use the preview generator app:

In case anybody is interested. I had no idea how to recreate the previews, as I had a lot of erroneous preview images. What I did was:

  • stop apache
  • make backup
  • remove the appdata/previews folder
  • run occ files:cleanup (not sure if this one is really necessary)
  • run occ files:scan-app-data (not sure if this one is really necessary)
  • start apache

all the previews get regenerated.