Fediverse => Bluesky: auto-generate embeds (with thumbnail images) for links?

[EdlReg]

I do not know if this is a general problem between platforms or if it is strictly an issue between Mastodon -> Bluesky, but whenever I post an article (or other external link) on Mastodon the thumbnail doesn't show up on Bluesky. You can see the link and click on it, but no thumbnail.
Would be great if this could be fixed.

[Tamschi]

This happens because in ActivityPub (Mastodon) link previews are generated by the receiver, but in Bluesky they are stored by the sender as part of the post itself. Bridgy Fed already handles this for web posts it seems (#1192).

Relevant Bluesky lexicons:

• app.bsky.feed.post (.embed)
• app.bsky.embed.external

[EdlReg]

Ok, my instance is Mastodon.nu if that is of any importance.

[Tamschi]

It's mainly the software and version that matters, as long as posts go through at all.

(The current Mastodon v4.3.1, in this case.)

[snarfed]

This is an interesting one! @Tamschi is broadly right: Bluesky/ATProto link previews (including thumbnail images) are explicit metadata in post objects. ActivityStreams 2 post objects can have similar link preview metadata, eg in the attachment field, but fediverse clients and servers like Mastodon often generate them from the first link in the post instead. When they get a post with an attachment, they halfway honor it and render it similarly, but usually without an image, so it looks like a second class citizen.

Take https://indieweb.social/users/snarfed/statuses/112582713947140513 as an example. I authored it inside Mastodon, and included a single URL in the text. Mastodon renders a link preview embed for that URL, in both the source instance and remote instances, but it federates it as an AS2 Note with no attachment value. The user-visible link preview is handled entirely outside AP.

I haven't done a comprehensive survey, but afaik at least some other popular fediverse servers, if not most, do the same thing.

So, the common case is that fediverse link previews are a non-standard heuristic, and I'm reluctant to bake that kind of thing into Bridgy Fed. I get that it might still be the right thing to do for UX though! So I'm torn.

(I do indeed do this for web => Bluesky, but that situation is very different, since the source post is a single specific web page.)

[snarfed]

More background on how fediverse servers, particularly Mastodon, prefer to generate their own link previews and don't really want (or trust) them in federated attachments: #958

[EdlReg]

Any progress on this issue? I think it should be a priority, since many Bluesky users are (understandably) hesitant to click on a shortened URL. See example below.

[snarfed]

No progress yet, sorry.

First step would be to decide that we want to apply this non-standard heuristic described above, specifically that if there are link(s) in the text and no explicit preview, we generate one automatically based on the first link. I don't love that, but I guess I'm ok with it.

After that, it's just the implementation work. PRs are welcome!

[EdlReg]

I can see why you're hesitant/reluctant, but as long as most fediverse clients and servers like Mastodon continue to generate previews from the first link in the post, it sounds like a good fix.
Unfortunately, I'm not a coder myself, but I'm happy to give feedback on design proposals, if that is of any help.

[Steviemac1]

Sorry, I hadn't seen/connected Flipboard URLs not generating an image with this. If I may show my naivety and ignorance and ask a possibly daft question. Can major platforms like Flipboard be persuaded to do anything different to make it work, or is that the wrong end to tackle the issue?

[Tamschi]

Interestingly, there seems to be ongoing work on Mastodon's end to federate link previews: https://www.theregister.com/2024/05/06/mastodon_delays_fix_ddos/

The discussion on that is here: mastodon/mastodon#23662

If they go ahead with standardising a federated link preview system, even if it's just a cached version without full trust, then that's likely something that Bridgy Fed could translate back and forth between the networks.

[snarfed]

Can major platforms like Flipboard be persuaded to do anything different to make it work, or is that the wrong end to tackle the issue?

Good question! I talk with people at Flipboard and many of the other big platforms pretty regularly. There are a number of options here, discussed above, but the conclusion right now is probably just to generate the previews ourselves.

[Steviemac1]

Thanks, just to add. I now see someone has noted that the bridged posts from Flipboard look like a bot and has added to a warning list. Small scale, but could be indicative of how viewers see the posts.

[Steviemac1]

There has been a slight change. More of a text preview now appears on posts from Flipboard, but no image as yet.

[snarfed]

Good eye! Yup, I shipped a first pass at this, it works, but doesn't include images yet. Working on those.

[Steviemac1]

Sounds like a plan! Thanks.

[EmilJacobs]

I see previews now 👀

[Steviemac1]

Me too, thank you for the fix. It looks so much better now. 🙌

[snarfed]

Rolling this back temporarily due to #1575, sorry. It'll be back soon!

[popet-master]

also, you'll want to mind the hashtag (induced) links in the bridged posts. I had a post from piaille.fr Masto that had a hashtag first thing, and it displayed on Bsky with the preview of piaille.fr 😁

[snarfed]

Updated and deployed again. Example:

• https://indieweb.social/@snarfed/113576299711842461
• https://bsky.app/profile/fedi.test.snarfed.org/post/3lca2dpcv4c32

[chaperon1234]

My bluesky account is
https://bsky.app/profile/chaperon.fedibird.com.ap.brid.gy
but these toot is not reflected in blue sky.

https://fedibird.com/@chaperon/113585855054825034
https://fedibird.com/@chaperon/113581312460836009

There are several other posts that have not been reflected in blueSky since the day the link preview feature of this issue was implemented.
It appears to be mainly Twitter and Bluesky links, but there are a few other posts that are not being reflected.
Do you know the cause?

[EdlReg]

Working great for me, toots with external links showing up with previews on Bluesky (my Mastodon account is on the instance Mastodon.nu, btw). Thank you for fixing this, @snarfed !

Haven't tried links to X or Bluesky, but for me that's of less importance than news sites etc.

[EmilJacobs]

Just a short addon to this: it works well for short posts that are bridged, but for posts with more than 300 characters, it doesn't. Could this still be fixed?

[snarfed]

@EmilJacobs right now, if a post is longer than 300 chars and we have to truncate it, we prioritize the link to the original post.

[popet-master]

on some posts, it seems that the image size in the mirrored post is not set as per the original, see e.g.
https://bsky.app/profile/politipet.piaille.fr.ap.brid.gy/post/3lcl3tpopwai2
vs
https://piaille.fr/@politipet/113601175324204315

[snarfed]

@popet-master yes! that's #1571