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):
You must log in or register to comment.
This was fixed on
lemmy.wtfa while ago but apparently this was still an issue onlemmy.worldwhich now has been fixed:https://lemmy.world/post/1421693
The
docker-compose.ymlI 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.
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.
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?
Exactly.
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:
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.
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.
This works:
This doesn’t work:
The difference between the two communities at lemmy.world, is that c/selfhosted has been around for a long time and c/xcode was created just a few days ago. It seems that only communities that initially connected with kbin.social work, but not new communities.
I see you have been discussing this with the people & mod of the GW2 magazine on kbin.social already. To me it really seems to be an issue on their side. As I mentioned above: I currently cannot subscribe from
feddit.deto their GW2 magazine, either.Update: I was now able to subscribe to their GW2 magazine from
feddit.de, but it does not display any posts.
I also found this
https://github.com/LemmyNet/lemmy-ui/issues/20
There is an environment variable
LEMMY_UI_DISABLE_CSP(default : false) to configurelemmy-ui. Do you set this on your instance or do you set aContent-Security-PolicxyHeader somewhere in your webserver/nginx config?I just use the settings as it is shown in the installation guide for Docker: https://join-lemmy.org/docs/en/administration/install_docker.html
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.
Brainstorming
- Thumbnail extraction definitely happens in the backend.
- But when does it happen?
- Only when creating the post?
- Or also when federating a post to a new instance?
- PR which replaced
iframely➡ https://github.com/LemmyNet/lemmy/pull/1706 - Now backend uses
fetch_site_metadata➡ https://github.com/LemmyNet/lemmy/blob/main/crates/api_common/src/request.rs - … which evaluates the opengraph (
og:*) meta tags from a linked HTML document whenever a post is created or updated
- Thumbnails do neither work on
lemmy.wtfnorlemmy.worldbut work onfeddit.de- Does
feddit.deextract the missing thumbnail when creating/updating the post? ➡ Yes, I think so - Or does it expect the thumbnail to be transmitted alongside the post? ➡ No, I don’t think so
- Does
lemmy.worlddoes not use cloudflare (I think) but they are also (likelemmy.wtf) using docker (I think)
Also Not Working on
lemmy.worldBut does on
feddit.deIt’s not only YT thumbnails which aren’t shown. This is your post about the free 24 slot bag as shown on
lemmy.wtf(no thumbnail),lemmy.world(no thumbnail) andfeddit.de(with thumbnail):- Thumbnail extraction definitely happens in the backend.
