View source for ActivityPub

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<span style="background:white; float:right;">[[File:activitypub.svg|frameless|128px|ActivityPub icon]]<br>[[File:w3c-logo.svg|frameless|128px|W3C logo]]</span>

'''<dfn>[https://www.w3.org/TR/activitypub/ ActivityPub]</dfn>''' is a decentralized social networking protocol ([[W3C]] Recommendation) developed in the [[Social Web Working Group]] based on [[pump.io]] and [[ActivityStreams]]. Conceptually they were all preceded by [[OStatus]]. It was  briefly known as <dfn>ActivityPump</dfn> before being renamed to ActivityPub.

* Latest published version: https://www.w3.org/TR/activitypub/
* Latest draft: https://w3c.github.io/activitypub/

[[File:w3c-spec-REC.svg|640px]]

__TOC__

== IndieWeb Examples ==
=== Matthias Pfefferle  ===
{{pfefferle}} has built the [[WordPress]] [https://wordpress.org/plugins/activitypub/ ActivityPub] and [https://wordpress.org/plugins/nodeinfo/ NodeInfo plugin]s which allows his WordPress sites to (at least partially) support the ActivityPub protocol so sites like [[Mastodon]] and other parts of the Fediverse view his sites as a federated member. Other sites using this method can be seen at https://the-federation.info/wordpress.
=== Aaron Parecki ===
{{aaronpk}} added initial support for [[ActivityPub]] to his website around 2018-07-04 in order to be able to receive likes & comments, reply to Mastodon users, and so that it can be followed from people using compatible software

As of 2018-07-23, {{aaronpk}} has about 64 followers from various ActivityPub profiles, and has a few posts that have received a mix of replies from Mastodon and other ActivityPub users.

* https://aaronparecki.com/2018/07/19/26/
* https://aaronparecki.com/2018/07/07/8/oauth

Nautilus:
* turned knowledge of implementing ActivityPub into a separate service that can be used to add ActivityPub to any website, the code is available as [https://github.com/aaronpk/Nautilus Nautilus] on GitHub.

=== Greg McVerry ===
{{jgmac1106}} uses:
* native ActivityPub support in [[Micro.blog]] which can be viewed @jgmac1106@stream.jgregorymcverry.com he can then send posts from his blog to his ActivityPub instance through [[Micro.blog]]

Previously used (quickthoughts.jgregorymcverry.com unresponsive as of 2023-05-25):
* Mastodon Plugin for [[Known]] which enables syndication:
** Added the Mastodon Plugin for [[Known]] to syndicate posts but also used [[Bridgy]] to create an instance of his blog at  @quickthoughts.jgregorymcverry.com@quickthoughts.jgregorymcverry.com.

=== Jan-Lukas Else ===
{{jlelse}} uses [[GoBlog]], which has native ActivityPub support.

=== Hammy Havoc ===
{{hammyhavoc}} added ActivityPub support on the [https://hammyhavoc.com Hammy Havoc blog] on 2023-01-01 via the ActivityPub WordPress plugin.

=== Ryan Barrett ===
{{snarfed}} uses [[Bridgy Fed]] to backfeed ActivityPub interactions from Mastodon etc to his site, eg the [https://snarfed.org/2019-10-22_mastodon-on-bridgy#comments interactions on this page] and [https://snarfed.org/about the followers list at the bottom of this page].

=== Lots more Bridgy Fed users ===
{{main|Bridgy_Fed#IndieWeb_Examples}}
Since 2019, many more folks have added ActivityPub support to their personal sites via Bridgy Fed.
* ...
* {{t}}
* ...

== Bridging ==

{{main|bridge#ActivityPub}}

=== Bridgy Fed ===

[[Bridgy Fed]] is a comprehensive service that translates ActivityPub feeds and interactions to/from IndieWeb sites and protocols.

=== ActivityPub Notifications to Webmention ===

Since Mastodon and other ActivityPub implementations often include Microformats on their permalinks, a shortcut for receiving comments from ActivityPub servers is to treat them as webmentions instead of doing the full Inbox processing normally required by ActivityPub.

When your ActivityPub inbox receives a notification:

* If <code>type</code> is <code>Create</code>
** and if <code>object.InReplyTo</code> is present and is a URL on your domain
*** then save <code>object.id</code> as "source"
*** save <code>object.InReplyTo</code> as "target"
*** send a webmention to your webmention endpoint with the source and target

Then your site's existing webmention handling will fetch and verify the ActivityPub source URL, and if there are Microformats on the page, will even look like a reply.

Example:
* Post permalink: https://aaronparecki.com/2018/07/01/9/
* Mastodon reply URL: https://mastodon.social/@aaronpk/100302258872089825

=== Sending an ActivityPub notification from an IndieWeb website ===

As more people and services in the IndieWeb build in support for ActivityPub, it's important to remember that competing communication options could happen. Here is a general top-level breakdown of sending an ActivityPub notification for a [[reply]] or [[like]].

The u-in-reply-to or u-like-of url will be referred to as the "targetUrl" below, and your post is referred to as the sourceUrl.

* Fetch the targetUrl via text/html, check for a [[webmention]] endpoint.
* If webmention endpoint exists, abort ActivityPub and send a [[webmention]] for sourceUrl to targetUrl
* If webmention endpoint does not exist, attempt to fetch the targetUrl as <code>application/activity+json</code>
** If targetUrl doesn't return JSON, targetUrl doesn't accept ActivityPub, abort.
** If targetUrl returns JSON, check for a top-level <code>@context</code> attribute. This can be an array or a string, check if it contains "<code>https://www.w3.org/ns/activitystreams</code>".
*** If targetUrl's JSON response does not return the right details, abort.
*** If targetUrl's JSON response returns the correct info, check the <code>attributedTo</code> attribute for the author's ActivityPub profile.
**** Fetch the author's ActivityPub profile url as <code>application/activity+json</code> and check top-level <code>inbox</code> attribute for the author's ActivityPub inbox endpoint.
**** Send an ActivityPub notification to the author's ActivityPub inbox endpoint.

==== Tips & Tricks for Sending ActivityPub notifications ====
* Mastodon requires that you include a "Mention" in the tags array, but you also need to include the person's <code>preferredUsername</code> in the post text to show it as a notification.
* Technically <code>attributedTo</code> can be an object, but this hasn't been seen in the wild yet.

== How To ==
(this section is a stub, please add links to How To articles for ActivityPub)
* Developer primer (in progress) on W3C wiki: https://www.w3.org/wiki/ActivityPub/Primer
* Funkwhale’s [https://docs.funkwhale.audio/developer/federation/index.html federation documentation] contains very clear examples of activities to be send around.
* [https://blog.joinmastodon.org/2018/06/how-to-implement-a-basic-activitypub-server/ How to Implement a Basic ActivityPub Server]

== Software ==
Open source software that supports ActivityPub:
* [[Mastodon]]
* [[PixelFed]]
* [[Pleroma]] and forks such as [[Akkoma]]
* [[WordPress ActivityPub plugin]]
* [[Drupal ActivityPub plugin]]
* [[WriteFreely]]
* [[microblog.pub]]
* [[OwnCast]]
* [[GoToSocial]]
* [[Lemmy]]
* [[Misskey]] and forks such as [[Calckey]]
* [[BookWyrm]]
* [[Takahē]]
* https://git.thebackupbox.net/actpub/

== Services == 
Services that support ActivityPub:
* [[Bridgy Fed]]
* [[micro.blog]]

== IndieWebCamp Sessions ==
* [[2018/NYC/activitypub]]
(pretty sure there's been more sessions, e.g. re: Bridging that was brainstormed and developed at [[2017]] or [[2018]])

== Criticism ==
(this section needs organizing into discrete rational criticisms, even better if they can be filed as issues on the specs and moved to an "Issues" section instead)
* {{citation
| title = ActivityPub - one protocol to rule them all?
| url = https://schub.io/blog/2018/02/01/activitypub-one-protocol-to-rule-them-all.html
| author = Dennis Schubert
| published = 2018-02-01
| archiveurl = https://web.archive.org/web/20181208062036/https://schub.io/blog/2018/02/01/activitypub-one-protocol-to-rule-them-all.html
}}
** Response: {{citation
| title = ActivityPub? Well, it’s not that bad
| url = https://feneas.org/activitypub-well-its-not-that-bad/
| author = Michael Vogel
| published = 2019-01-09
| archiveurl = http://web.archive.org/web/20190209024932/https://feneas.org/activitypub-well-its-not-that-bad/
}}
* {{citation
| title = ActivityPub - Final thoughts, one year later
| url = https://schub.io/blog/2019/01/13/activitypub-final-thoughts-one-year-later.html
| author = Dennis Schubert
| published = 2019-01-13
| archiveurl = https://web.archive.org/web/20190202142206/https://schub.io/blog/2019/01/13/activitypub-final-thoughts-one-year-later.html
}}
* 2018-07-30 [http://beesbuzz.biz/blog/2535-ActivityPub-hot-take ActivityPub hot take] <blockquote>This isn’t creating a distributed network, this is creating a whole bunch of massive points of failure. And these failures grow exponentially as more failures happen. Its very nature also makes it so that it’s much more difficult for this data to be migrated; look at what happened when [[witches.town]] went down, or when scifi.fyi’s certificate expired [Ed.: for ~ a day https://scifi.fyi/@BrokenBiscuit/100426278316164570], and the effects this had on all other instances regardless of the users of those instances. And spinning up an instance is expensive, and that cost rises with the number of instances out there.</blockquote>
* 2018-08-07 Thread from author of [[litepub]] draft specification, provides background frustration and motivations for a variant protocol: https://pleroma.site/notice/2962026
** "activitypub is a crummy protocol, largely designed by committee, largely intended to make W3C brass happy by cargoculting even more of their crummy technology into it.<br><br>we need to fork this shit today and purge W3C from activitypub.  it's the only conclusion i keep coming to after trying to read their specs." [https://pleroma.site/users/kaniini @kaniini] August 7, 2018

== See Also ==
* https://activitypub.com/ which apparently redirects to https://activitypub.rocks/
* https://github.com/go-fed/presentations/tree/master/2018/go-activitypub-journey
* https://blog.joinmastodon.org/2018/07/how-to-make-friends-and-verify-requests/
* https://octodon.social/web/statuses/100527636732474823
* [[Bridgy Fed]]
* [https://wordpress.org/plugins/activitypub/ ActivityPub plugin for WordPress] from {{pfefferle}}
* [[CommonsPub]]
* https://twitter.com/tinysubversions/status/1204494753066209280
** "I just released a small ActivityPub debugging tool. It's hosted on @glitch and the idea is that an AP developer can simply remix the project and instantly have their own tiny AP server from which they can send arbitrary test messages.<br><br>https://tinysubversions.com/notes/activitypub-tool/" [https://tinysubversions.com @tinysubversions] December 10, 2019
* [https://moodle.com/news/moodlenet-what-is-a-federated-social-network/ MoodleNet: What is a federated social network?]
* [[WriteFreely]]
* [[PixelFed]]
* https://socialhub.activitypub.rocks/c/software/14
* [https://codeberg.org/fediverse/delightful-activitypub-development/ a repository of libraries and projects]
* [https://github.com/dariusk/express-activitypub Sample Express implementation]
* [[microblog.pub]]
* [https://goldfish.social/ Goldfish], a federated service similar to [[TikTok]] or [[Vine]]
* Limitation: upon "[[follow]]ing" someone, you don’t see their recent/past posts, unlike the UX of feed readers, Podcast apps, literally every other UX where you follow someone and immediately see a list of the recent posts / episodes / published content. https://twitter.com/stevehunt4hiop/status/1589913026832236545 see related issue: https://github.com/mastodon/mastodon/issues/1547
** "Here is another surprise. If you follow someone on another instance, you will not get access to their previous posts, unless it so happens that they were already being federated to your instance. Your instance will start to collect their new activity but will never go back..." [http://hiopcouncillors.org @stevehunt4hiop] November 8, 2022
* https://github.com/mwt/apfollow/ Code and buttons for creating ActivityPub Follow me interface
* ^ apfollow sample service didn’t work with a fediverse address (user & instance) that uses [[Bridgy Fed]] ({{t}} just got an error from it by trying e.g. https://apfollow.mwt.me/?user=tantek.com&instance=tantek.com which returned a plain text error page of “Couldn't find user”)
* https://github.com/davecheney/pub
* Why NOT to add AP support to your site: 2023-01-03 [https://kevquirk.com/does-a-blog-need-to-integrate/ Does a Blog Need to Integrate?] <blockquote>Without a lot of work, a website won’t have the level of functionality a Mastodon account has. <br/><br/>So if the “integration” at this point is simply a way to auto-post to Mastodon (or any ActivityPub service) where’s the value over something like Zapier, or IFTTT? I don’t see it.</blockquote>
* Why avoid JSON-LD in your ActivityPub implementations: 2018-11-12 [https://ariadne.space/2018/11/12/pleroma-litepub-activitypub-and-json-ld/ Pleroma, LitePub, ActivityPub and JSON-LD] <blockquote>… it is a critical obligation of federated social networking service developers to ensure that handling of data is done in the most secure way possible, built on proven fundamentals. I view the inclusion of JSON-LD in the ActivityPub and ActivityStreams 2.0 standards to be harmful toward that obligation.</blockquote>
* Criticism: https://ruby.social/@benubois/111267597245152198
** "@manton I gave up on even consuming ActivityPub. It’s an ambitious idea, but wow is it ever complex, verbose, abstract and under defined. It also feels like the wrong abstraction for micropost-like things. JSON Feed and Micropub are much more ergonomic." [https://ruby.social/@benubois @benubois] October 20, 2023
* Criticism of RDFisms in AP: https://hachyderm.io/@hrefna/111634273843633052
** "I am not working with AP from a graph database.I am not working against a RDF data modelI am not dealing with RDF projectionsI am not an academic who is working with ontologies From a standards perspective: Every single time weirdness from RDF leaks into JSON, it adds complexity to downstream implementations. If your spec is entirely based on RDF that's one thing. But if your spec disclaims being based on RDF and says "only for extensions," then you can't have your cake and eat it too." [https://hachyderm.io/@hrefna @hrefna] December 24, 2023
* [https://maho.dev/2024/02/a-guide-to-implement-activitypub-in-a-static-site-or-any-website/ A guide to implement ActivityPub in a static site (or any website)]