Visibility ↔ To/Cc mapping

Statuses in the Mastodon API have a visibility field; Notes in ActivityPub have To/Cc/Bto/Bcc/Audience fields which provide much the same functionality. I have been trying to figure out how they map to each other:

Mastodon visibility To Cc
public contains public n/a
unlisted n/a contains public
private contains actor’s followers n/a
direct contains anyone in mentions n/a
limited fallback? fallback?

Read top to bottom. “Contains public” means there’s a non-empty intersection with the set [https://www.w3.org/ns/activitystreams#Public, as:Public, Public].

Is this reasonable?

This should probably be moved to the Software/Mastodon category, since it’s not really a question about ActivityPub.

But in any case, Mastodon’s visibility scopes are a custom thing and this is generally how they map:

  • public = to: [public], cc: [followers, mentions]
  • unlisted = cc: [public, followers, mentions]
  • followers-only = to: [followers], cc: [mentions]
  • direct = to: [mentions]

Incoming posts are converted heuristically. There is no concept of “unlisted” visibility or scope in ActivityPub by default – all addressing uses to/cc which should immediately be mapped to inboxes by the server.

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Thanks. Incoming posts retain their to/cc data, notwithstanding the conversion?

@marnanel mastodon does not store any original ActivityPub data, it just processes it into what the client will use.