Does anybody know why and when thumbnails for YouTube videos are shown or not? It appears to depend on the lemmy instance the posts are served from:

Without Thumbnails

With Thumbnails

Update: It’s not only YT thumbnails which aren’t shown. This is your post about the free 24 slot bag as shown on lemmy.wtf (without thumbnail), lemmy.world (without thumbnail) and feddit.de (with thumbnail):

  • Necropola❌OPEnglish
    3•1 year ago

    This was fixed on lemmy.wtf a while ago but apparently this was still an issue on lemmy.world which now has been fixed:

    https://lemmy.world/post/1421693

    The docker-compose.yml I copied from somewhere when setting up lemmy.world apparently was missing the external network for the pictrs container… So pictrs was working, as long as it got the images via Lemmy. Getting the images via URL didn’t work…

    Note: This only fixes new posts. In order to fix old posts you need to edit/save them once.

  • MeldrikMEnglish
    2•2 years ago

    I’ve been trying to troubleshoot it. It makes very little sense to me, that it doesn’t show thumbnails from local posts on lemmy.wtf, but if you can via another instance, the thumbnails show up.

    • Necropola❌OPEnglish
      3•2 years ago

      But you are getting the same results as me when trying the links? The first 2 have thumbnails and the last 2 don’t, right?

        • Necropola❌OPEnglish
          3•2 years ago

          That’s really weird. I already went through the issue tracker on GitHub for both the lemmy backend as well as the frontend, but couldn’t find anything. I also checked the documentation whether there is a configuration option somewhere. Nothing.

          My guess is that the thumbnail is extracted (read from the opengraph tag available via the posted URL) in the frontend (and not the backend). (wrong guess)

          The only thing I could find on the issue tracker which might be related is this:

          https://github.com/LemmyNet/lemmy-ui/issues/709

          • MeldrikMEnglish
            1•2 years ago

            I have no idea why it is happening. The only thing I can think of is Cloudflare tunnel, but why would that keep the thumbnails from loading? I send a message to the admin of Lemmy.world.

            edit: I am also trying to troubleshoot why users from kbin.social can’t subscribe to here and vice versa.

            • Necropola❌OPEnglish
              3•2 years ago

              I was able to subscribe from lemmy.world to kbin.social (yesterday or the day before). I tried it on another account from feddit.de today and it did not work. My guess is a problem at kbin.social.

        • Necropola❌OPEnglish
          3•2 years ago

          I also found this

          https://github.com/LemmyNet/lemmy-ui/issues/20

          There is an environment variable LEMMY_UI_DISABLE_CSP (default : false) to configure lemmy-ui. Do you set this on your instance or do you set a Content-Security-Policxy Header somewhere in your webserver/nginx config?

            • Necropola❌OPEnglish
              3•2 years ago

              OK. Looks like the CSP headers are the same on working and not working instances.

              What I found surprising is that chrome loads the thumbnail without accessing the actual YT URL (contrary to what I expected) from the “pictrs” server of the instance serving the post. Which means that the thumbnail gets only extracted once and is then stored along with the post.