ActivityPub

 

 ActivityPub  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 ActivityPump before being renamed to ActivityPub.


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

Matthias Pfefferle
has built the WordPress ActivityPub and NodeInfo plugins 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
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, 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 Nautilus on GitHub.

Greg McVerry
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
has native ActivityPub support on his blog using a custom implementation, that sends JSON Feed updates to followers.

Hammy Havoc
added ActivityPub support on the Hammy Havoc blog on 2023-01-01 via the ActivityPub WordPress plugin.

Ryan Barrett
uses Bridgy Fed to backfeed ActivityPub interactions from Mastodon etc to his site, eg the interactions on this page and the followers list at the bottom of this page.

Lots more Bridgy Fed users
Since 2019, many more folks have added ActivityPub support to their personal sites via Bridgy Fed.
 * undefined
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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  is
 * and if  is present and is a URL on your domain
 * then save  as "source"
 * save  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
 * If targetUrl doesn't return JSON, targetUrl doesn't accept ActivityPub, abort.
 * If targetUrl returns JSON, check for a top-level  attribute. This can be an array or a string, check if it contains " ".
 * If targetUrl's JSON response does not return the right details, abort.
 * If targetUrl's JSON response returns the correct info, check the  attribute for the author's ActivityPub profile.
 * Fetch the author's ActivityPub profile url as  and check top-level   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  in the post text to show it as a notification.
 * Technically  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 federation documentation contains very clear examples of activities to be send around.
 * 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
(pretty sure there's been more sessions, e.g. re: Bridging that was brainstormed and developed at 2017 or 2018)
 * 2018/NYC/activitypub

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)
 * Response:
 * 2018-07-30 ActivityPub hot take "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."
 * 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. 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." @kaniini August 7, 2018
 * 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. 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." @kaniini August 7, 2018