Hi @devnull . I haven't been following the forum topic federation discussions very closely, so this may be a silly question. Are forum topics going to be fully federated or just replicated (which is not quite the same thing, even for 2-way sync)? For example, if in the future there are 1000's of NodeBB instances running and there's a topic X, is it possible that the posts for that topic could be coming from multiple NodeBB instances (or other instance implementations)? If so, a topic-level canonical link will not work. Google currently indexes individual Mastodon posts (at least some of them, not sure about all of them). The AP Note identifier is the canonical URL in this case. (Google also indexes actor profiles in some cases, but that's a different discussion. ) FWIW, this is the canonical link I see for this topic: I'm guessing the canonical link you quoted is on the NodeBB side? Since these are different canonical links, I'd expect that Google will consider these (SocialHub and NodeBB topics) to be different web resources with mostly replicated content.