Preview generation on Nextcloud 19


after upgrading to Nextcloud 19, I saw weird behavior on preview generations.
I’d like to know if someone else saw it too.

One issue is that it generates previews for all files (also .pdf which should not be the default behavior from what I know…). Even if my config file contains:

‘enabledPreviewProviders’ =>
array (
0 => ‘OC\Preview\PNG’,
1 => ‘OC\Preview\JPEG’,
2 => ‘OC\Preview\GIF’,

I get previews not only for images. Shouldn’t I get previews only for those 3 types of file?

Another issue is that the web client doesn’t find some previews when loading a folder and it gets stuck untill the 404 timeout on that failed get request, actually not showing the folder list for 10 or more seconds. I don’t know yet why some previews are actually not available…


Am I really the only one with this problem about thumbnails generation?

Hi! I’m struggling with preview generation too - but have not tried to limit it as you do.

My problem is the extremely high disk usage of the generated previews, so I will try to do what you do; only create previews for images.

I’m wondering if you maybe have old previews from before you limited preview generation to only PNG, JPEG and GIF?

You can delete all previews and generate them anew. That’ll take a while of course, but maybe could fix the issue?

Here’s a few potentially useful links:

1 Like

Ty for your answer, @Ferdinand.
Actually my problem is that, even if I delete all previews, when I enter a folder with .odt, .pdf, etc. files the thumbnail gets created again, in spite of my config file, as shown above. It doesn’t happen on Nextcloud 18.
That wouldn’t be a problem in general since I always wanted all kinds of thumbnails so far, but it looks like with Nextcloud 19 another issue comes up, that is the fact that sometimes a preview is not found (404 error on Firefox developer console) but this 404 arrives after many seconds so the page is shown after 10-20 secs when one of these previews in not found, and that’s quite annoying. This last issue could be due to my system, that’s why I asked if anyone saw it, or it’s only me.