diff --git a/content/en/spec/activitypub.md b/content/en/spec/activitypub.md
index f8ff7feb..5ab4dcf0 100644
--- a/content/en/spec/activitypub.md
+++ b/content/en/spec/activitypub.md
@@ -7,10 +7,6 @@ menu:
     parent: spec
 ---
 
-{{< hint style="warning" >}}
-Sample payloads will be added at a future date.
-{{< /hint >}}
-
 ## Status federation {#status}
 
 {{< caption-link url="https://github.com/mastodon/mastodon/blob/main/app/lib/activitypub/activity.rb" caption="app/lib/activitypub/activity.rb" >}}
@@ -29,21 +25,21 @@ Like
 Announce
 : Transformed into a boost on a status
 
-Flag
-: Transformed into a report to the moderation team.
-
 Update
-: Refresh vote count on polls. As of Mastodon 3.5.0, can be used to edit statuses when the `updated` timestamp is present.
+: Refresh vote count on polls. As of Mastodon 3.5.0: edit statuses when the `updated` timestamp is present.
 
 Undo
 : Undo a previous Like or Announce.
 
+Flag
+: Transformed into a report to the moderation team. See the [Reports](#Flag) extension for more information.
+
 ### Payloads
 
 The first-class Object types supported by Mastodon are `Note` and `Question`.
 
 - Notes are transformed into regular statuses.
-- Questions are transformed into a poll status.
+- Questions are transformed into a poll status. See the [Polls](#Question) extension for more information.
 
 Some other Object types are converted as best as possible:
 
@@ -56,6 +52,64 @@ Some other Object types are converted as best as possible:
 
 The transformer uses `content` if available, or `name` if not, in order to generate status text. The `url` will be appended. The `summary` property will be used as the CW text. The `icon` will be used as a thumbnail.
 
+### HTML sanitization {#sanitization}
+
+{{< caption-link url="https://github.com/mastodon/mastodon/blob/main/lib/sanitize_ext/sanitize_config.rb" caption="lib/sanitize_ext/sanitize_config.rb" >}}
+
+Mastodon sanitizes incoming HTML in order to not break assumptions for API client developers. Supported elements will be kept as-is, and unsupported elements will be converted or removed. Supported attributes will be kept, and all other attributes will be stripped. The following elements and attributes are supported:
+ 
+- `<p>`
+- `<span>` (`class`)
+- `<br>`
+- `<a>` (`href`, `rel`, `class`)
+- lists will be converted to `<p>`, and list items will be separated with `<br>`
+
+Since Mastodon v4.2, the following elements and attributes are supported:
+
+- `<p>`
+- `<span>` (`class`)
+- `<br>`
+- `<a>` (`href`, `rel`, `class`)
+- `<del>`
+- `<pre>`
+- `<code>`
+- `<em>`
+- `<strong>`
+- `<b>`
+- `<i>`
+- `<u>`
+- `<ul>`
+- `<ol>` (`start`, `reversed`)
+- `<li>` (`value`)
+- `<blockquote>`
+- headings will be converted to `<strong>` and then wrapped in `<p>`
+ 
+The sanitizer will keep classes if they begin with microformats prefixes or are semantic classes:
+
+- h-*
+- p-*
+- u-*
+- dt-*
+- e-*
+- mention
+- hashtag
+- ellipsis
+- invisible
+
+Links will be kept if the protocol is supported, and converted to text otherwise. The following link protocols are supported:
+
+- http
+- https
+- dat
+- dweb
+- ipfs
+- ipns
+- ssb
+- gopher
+- xmpp
+- magnet
+- gemini
+
 ### Properties used
 
 content
@@ -68,7 +122,7 @@ summary
 : Used as CW text
 
 sensitive
-: Used to determine whether status media or text should be hidden by default
+: Used to determine whether status media or text should be hidden by default. See the [Sensitive content](#sensitive) extension section for more information about `as:sensitive`
 
 inReplyTo
 : Used for threading a status as a reply to another status
@@ -82,25 +136,17 @@ url
 attributedTo
 : Used to determine the profile which authored the status
 
-updated
-: Used to display the "last edited at" timestamp in the UI to indicate to the user that a status has been edited. Required before an Update activity will be processed. To prevent against race conditions, Mastodon will only process Update payloads with an `updated` timestamp greater than the currently known last `updated` time.
-
 to/cc
-: Used to determine audience and visibility of a status.
-  - Public statuses have the `as:Public` magic collection in `to`
-  - Unlisted statuses have the `as:Public` magic collection in `cc`
-  - Followers-only statuses have an actor's follower collection in `to` or `cc`, but do not include the `as:Public` magic collection
-  - Private statuses have actors in `to` or `cc`, at least one of which is not `Mention`ed in `tag`
-  - Direct statuses have actors in `to` or `cc`, all of which are `Mention`ed in `tag`
+: Used to determine audience and visibility of a status, in combination with mentions. See [Mentions for adddressing and notifications](#Mention)
 
 tag
 : Used to mark up mentions and hashtags.
 
 tag[].type
-: Either `Mention` or `Hashtag` is currently supported
+: Either `Mention`, `Hashtag`, or `Emoji` is currently supported. See the [Hashtag](#Hashtag) and [Custom emoji](#Emoji) extension sections for more information
 
 tag[].name
-: The plain-text Webfinger address of a profile Mention (`@user` or `@user@domain`), or the plain-text Hashtag (`#tag`)
+: The plain-text Webfinger address of a profile Mention (`@user` or `@user@domain`), or the plain-text Hashtag (`#tag`), or the custom Emoji shortcode (`:thounking:`)
 
 tag[].href
 : The URL of the actor or tag
@@ -156,24 +202,24 @@ Accept/Reject
 Add/Remove
 : Manage pinned posts and featured collections.
 
-Block
-: Signal to a remote server that they should hide your profile from that user. Not guaranteed.
-
-Flag
-: Report user
-
 Update
 : Refresh account details
 
-Move
-: Migrate followers from one account to another. Requires alsoKnownAs to be set in both directions.
-
 Delete
 : Remove an account from the database, as well as all of their statuses.
 
 Undo
 : Undo a previous Follow, Accept Follow, or Block.
 
+Block
+: Signal to a remote server that they should hide your profile from that user. Not guaranteed. See [Remote blocking](#Block) for more information.
+
+Flag
+: Report a user to their moderation team. See the [Reports](#Flag) extension for more information.
+
+Move
+: Migrate followers from one account to another. Requires `alsoKnownAs` to be set on the new account pointing to the old account.
+
 ### Properties used
 
 preferredUsername
@@ -218,82 +264,241 @@ alsoKnownAs
 published
 : When the profile was created.
 
-
-## HTML sanitization {#sanitization}
-
-{{< caption-link url="https://github.com/mastodon/mastodon/blob/main/lib/sanitize_ext/sanitize_config.rb" caption="lib/sanitize_ext/sanitize_config.rb" >}}
-
- Mastodon sanitizes incoming HTML in order to not break assumptions for API client developers. Supported elements include `<p>`, `<span>`, `<br>`, and `<a>`. Unsupported elements will be converted to `<p>`.The sanitizer will keep classes if they begin with microformats prefixes or are semantic classes:
-
-- h-*
-- p-*
-- u-*
-- dt-*
-- e-*
-- mention
-- hashtag
-- ellipsis
-- invisible
-
-## JSON-LD Namespacing {#namespaces}
+## JSON-LD Contexts and Extensions {#contexts}
 
 {{< caption-link url="https://github.com/mastodon/mastodon/blob/main/app/lib/activitypub/adapter.rb" caption="app/lib/activitypub/adapter.rb" >}}
 
 ### Mastodon extensions (`toot:`) {#toot}
 
+Base URI: `http://joinmastodon.org/ns#`
+
 Contains definitions for Mastodon features.
 
-- toot:Emoji
-- toot:IdentityProof
-- toot:blurhash
-- toot:focalPoint
-- toot:featured
-- toot:featuredTags
-- toot:discoverable
-- toot:suspended
-- toot:votersCount
+- toot:Emoji (`http://joinmastodon.org/ns#Emoji`)
+- toot:IdentityProof (`http://joinmastodon.org/ns#IdentityProof`)
+- toot:blurhash (`http://joinmastodon.org/ns#blurhash`)
+- toot:focalPoint (`http://joinmastodon.org/ns#focalPoint`)
+- toot:featured (`http://joinmastodon.org/ns#featured`)
+- toot:featuredTags (`http://joinmastodon.org/ns#featuredTags`)
+- toot:discoverable (`http://joinmastodon.org/ns#discoverable`)
+- toot:suspended (`http://joinmastodon.org/ns#suspended`)
+- toot:votersCount (`http://joinmastodon.org/ns#votersCount`)
 
 ### ActivityStreams extensions (`as:`) {#as}
 
+Base URI: `https://www.w3.org/ns/activitystreams#`
+
 Contains ActivityStreams extended properties that have been proposed but not officially adopted yet.
 
-- as:Hashtag
-- as:alsoKnownAs
-- as:manuallyApprovesFollowers
-- as:movedTo
-- as:sensitive
+- as:Hashtag (`https://www.w3.org/ns/activitystreams#Hashtag`)
+- as:manuallyApprovesFollowers (`https://www.w3.org/ns/activitystreams#manuallyApprovesFollowers`)
+- as:movedTo (`https://www.w3.org/ns/activitystreams#movedTo`)
+- as:sensitive (`https://www.w3.org/ns/activitystreams#sensitive`)
 
-### W3ID Security Vocabulary (`sec:`) {#sec}
-
-Contains properties used for HTTPS Signatures and Linked Data Signatures. Also used for identity proofs. See [Security]({{< relref "spec/security" >}}) for more information.
-
-- sec:publicKey
-- sec:publicKeyPem
-- sec:owner
-- sec:signature
-- sec:signatureValue
-
-#### W3ID Identity
-
-Contains a collection of terms from various namespaces, used for Linked Data Signatures.
-
-- dc:creator
-- dc:created
-- sec:signature
-- sec:signatureValue
-
-### schema.org extensions (`schema:`) {#schema}
+### Schema.org extensions (`schema:`) {#schema}
 
 Contains properties used for profile metadata.
 
-- schema:PropertyValue
-- schema:value
+Base URI: `http://schema.org#` (incorrect; should be `https://schema.org/`)
 
-## Extensions
+- [schema:PropertyValue (`http://schema.org#PropertyValue`, should be `https://schema.org/PropertyValue`)](https://schema.org/PropertyValue)
+- [schema:value (`http://schema.org#value`, should be `https://schema.org/value`)](https://schema.org/value)
+
+### W3ID Security Vocabulary (`sec:`) {#sec}
+
+Context: [`https://w3id.org/security/v1`](https://w3id.org/security/v1)
+
+Used for HTTPS Signatures. Also used for identity proofs. See [Security]({{< relref "spec/security" >}}) for more information.
+
+- [sec:publicKey (`https://w3id.org/security#publicKey`)](https://w3id.org/security#publicKey)
+- [sec:publicKeyPem (`https://w3id.org/security#publicKeyPem`)](https://w3id.org/security#publicKeyPem)
+- [sec:owner (`https://w3id.org/security#owner`)](https://w3id.org/security#owner)
+- [sec:signature (`https://w3id.org/security#signature`)](https://w3id.org/security#signature)
+- [sec:signatureValue (`https://w3id.org/security#signatureValue`)](https://w3id.org/security#signatureValue)
+
+#### W3ID Identity
+
+Context: [`https://w3id.org/identity/v1`](https://w3id.org/identity/v1) (offline)
+
+Used for Linked Data Signatures. See [Security > Linked Data Signatures]({{< relref "spec/security#ld" >}}) for more information.
+
+- [dc:creator (`http://purl.org/dc/terms/creator`)](http://purl.org/dc/terms/creator)
+- [dc:created (`http://purl.org/dc/terms/created`)](http://purl.org/dc/terms/created)
+- [sec:signature (`https://w3id.org/security#signature`)](https://w3id.org/security#signature)
+- [sec:signatureValue (`https://w3id.org/security#signatureValue`)](https://w3id.org/security#signatureValue)
+
+## Extensions defined using ActivityStreams vocabulary
+
+While the Activity Vocabulary defines a wide range of types and terms, ActivityPub only defines side effects for a subset of them. The following activity types have the following side effects when received in a Mastodon inbox.
+
+### Remote blocking (`Block`) {#Block}
+
+ActivityPub defines the `Block` activity for client-to-server (C2S) use-cases, but not for server-to-server (S2S) -- it recommends that servers SHOULD NOT deliver Block activities to their `object`. However, Mastodon will send this activity when a local user blocks a remote user. When Mastodon receives a `Block` activity where the `object` is an actor on the local domain, it will interpret this as a signal to hide the actor's profile and posts from the local user, as well as disallowing mentions of that actor by that local user.
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/bd06bb61-01e0-447a-9dc8-95915db9aec8",
+  "type": "Block",
+  "actor": "https://mastodon.example/users/alice",
+  "object": "https://example.com/~mallory",
+  "to": "https://example.com/~mallory"
+}
+```
+
+### Reporting profiles and posts (`Flag`) {#Flag}
+
+To report profiles and/or posts on remote servers, Mastodon will send a `Flag` activity from the instance actor. The `object` of this activity contains the user being reported, as well as any posts attached to the report. If a comment is attached to the report, it will be used as the `content` of the activity.
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/ccb4f39a-506a-490e-9a8c-71831c7713a4",
+  "type": "Flag",
+  "actor": "https://mastodon.example/actor",
+  "content": "Please take a look at this user and their posts",
+  "object": [
+    "https://example.com/users/1",
+    "https://example.com/posts/380590",
+    "https://example.com/posts/380591"
+  ],
+  "to": "https://example.com/users/1"
+}
+```
+
+### Account migration (`Move`) {#Move}
+
+Mastodon uses the Move activity to signal that an account has migrated to a different account. For the migration to be considered valid, Mastodon checks that the new account has defined an alias pointing to the old account (via the `alsoKnownAs` property).
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/users/alice#moves/1",
+  "actor": "https://mastodon.example/users/alice",
+  "type": "Move",
+  "object": "https://mastodon.example/users/alice",
+  "target": "https://alice.com/users/109835986274379",
+  "to": "https://mastodon.example/users/alice/followers"
+}
+```
+
+### Polls {#Question}
+
+{{< caption-link url="https://www.w3.org/TR/activitystreams-vocabulary/#questions" caption="Activity Vocabulary §5.4 - Representing Questions" >}}
+
+The ActivityStreams Vocabulary specification describes loosely (non-normatively) how a question might be represented. Mastodon's implementation of polls is somewhat inspired by this section. The following implementation details can be observed:
+
+- `Question` is used as an `Object` type instead of as an `IntransitiveActivity`; rather than being sent directly, it is wrapped in a `Create` just like any other status.
+- Poll options are serialized using `oneOf` or `anyOf` as an array.
+  - Each item in this array has no `id`, has a `type` of `Note`, and has a `name` representing the text of the poll option.
+  - Each item in this array also has a `replies` property, representing the responses to this particular poll option. This node has no `id`, has a `type` of `Collection`, and has a `totalItems` property representing the total number of votes received for this option.
+
+```json
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "votersCount": "http://joinmastodon.org/ns#votersCount"
+    }
+  ],
+  "id": "https://mastodon.example/users/alice/statuses/1009947848598745",
+  "type": "Question",
+  "content": "What should I eat for breakfast today?",
+  "published": "2023-03-05T07:40:13Z",
+  "endTime": "2023-03-06T07:40:13Z",
+  "votersCount": 7,
+  "anyOf": [
+    {
+      "type": "Note",
+      "name": "apple",
+      "replies": {
+        "type": "Collection",
+        "totalItems": 3
+      }
+    },
+    {
+      "type": "Note",
+      "name": "orange",
+      "replies": {
+        "type": "Collection",
+        "totalItems": 7
+      }
+    },
+    {
+      "type": "Note",
+      "name": "banana",
+      "replies": {
+        "type": "Collection",
+        "totalItems": 6
+      }
+    }
+  ]
+}
+```
+
+- Poll votes are serialized as `Create` activities, where the `object` is a `Note` with a `name` that exactly matches the `name` of the poll option. The `Note.inReplyTo` points to the URI of the `Question` object.
+  - For multiple-choice polls, multiple activities may be sent. Votes will be counted if you have not previously voted for that option.
+
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/users/bob#votes/827163/activity",
+  "to": "https://mastodon.example/users/alice",
+  "actor": "https://mastodon.example/users/bob",
+  "type": "Create",
+  "object": {
+    "id": "https://mastodon.example/users/bob#votes/827163",
+    "type": "Note",
+    "name": "orange",
+    "attributedTo": "https://mastodon.example/users/bob",
+    "to": "https://mastodon.example/users/alice",
+    "inReplyTo": "https://mastodon.example/users/alice/statuses/1009947848598745"
+  }
+}
+```
+```json
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/users/bob#votes/827164/activity",
+  "to": "https://mastodon.example/users/alice",
+  "actor": "https://mastodon.example/users/bob",
+  "type": "Create",
+  "object": {
+    "id": "https://mastodon.example/users/bob#votes/827164",
+    "type": "Note",
+    "name": "banana",
+    "attributedTo": "https://mastodon.example/users/bob",
+    "to": "https://mastodon.example/users/alice",
+    "inReplyTo": "https://mastodon.example/users/alice/statuses/1009947848598745"
+  }
+}
+```
+
+### Mentions for addressing and notifications {#Mention}
+
+{{< caption-link url="https://www.w3.org/TR/activitystreams-vocabulary/#microsyntaxes" caption="Activity Vocabulary §5.6 - Mentions, Tags, and Other Common Social Microsyntaxes" >}}
+
+In the ActivityStreams Vocabulary, `Mention` is a subtype of `Link` that is intended to represent the microsyntax of @mentions. The `tag` property is intended to add references to other Objects or Links. For Link tags, the `name` of the Link should be a substring of the natural language properties (`name`, `summary`, `content`) on that object. Wherever such a substring is found, it can be transformed into a hyperlink reference to the `href`.
+
+However, Mastodon also uses `Mention` tags for addressing in some cases. Based on the presence or exclusion of Mention tags, and compared to the explicitly declared audiences in `to` and `cc`, Mastodon will calculate a visibility level for the post. Additionally, Mastodon requires Mention tags in order to generate a notification. (The mentioned actor must still be included within `to` or `cc` explicitly in order to receive the post.)
+
+- `public`: Public statuses have the `as:Public` magic collection in `to`
+- `unlisted`: Unlisted statuses have the `as:Public` magic collection in `cc`
+- `private`: Followers-only statuses have an actor's follower collection in `to` or `cc`, but do not include the `as:Public` magic collection
+- `limited`: Limited-audience statuses have actors in `to` or `cc`, at least one of which is not `Mention`ed in `tag`
+- `direct`: Mentions-only statuses have actors in `to` or `cc`, all of which are `Mention`ed in `tag`
+
+{{< caption-link url="https://github.com/mastodon/mastodon/blob/main/app/lib/activitypub/activity/create.rb" caption="app/lib/activitypub/activity/create.rb" >}}
+
+{{< caption-link url="https://github.com/mastodon/mastodon/blob/main/app/lib/activitypub/parser/status_parser.rb" caption="app/lib/activitypub/parser/status_parser.rb" >}}
+
+## Extensions not defined by ActivityStreams
+
+The following features are defined using properties and types that are not defined by ActivityStreams.
 
 ### Public key {#publicKey}
 
-Public keys are used for HTTPS Signatures and Linked Data Signatures. This is implemented using an extra property `publicKey` on actor objects. See [Security]({{< relref "spec/security" >}}) for more information. Example:
+Public keys are used for HTTP Signatures and Linked Data Signatures. This is implemented using an extra property `publicKey` on actor objects. See [Security]({{< relref "spec/security" >}}) for more information.
 
 ```json
 {
@@ -313,16 +518,15 @@ Public keys are used for HTTPS Signatures and Linked Data Signatures. This is im
 
 ### Featured collection {#featured}
 
-What is known in Mastodon as “pinned statuses”, or statuses that are always featured at the top of people’s profiles, is implemented using an extra property `featured` on the actor object that points to a `Collection` of objects. Example:
+What is known in Mastodon as “pinned statuses”, or statuses that are always featured at the top of people’s profiles, is implemented using an extra property `featured` on the actor object that points to a `Collection` of objects.
 
 ```json
 {
   "@context": [
     "https://www.w3.org/ns/activitystreams",
     {
-      "toot": "http://joinmastodon.org/ns#",
       "featured": {
-        "@id": "toot:featured",
+        "@id": "http://joinmastodon.org/ns#featured",
         "@type": "@id"
       }
     }
@@ -343,9 +547,8 @@ Mastodon allows users to feature specific hashtags on their profile for easy bro
   "@context": [
     "https://www.w3.org/ns/activitystreams",
     {
-      "toot": "http://joinmastodon.org/ns#",
       "featuredTags": {
-        "@id": "toot:featuredTags",
+        "@id": "http://joinmastodon.org/ns#featuredTags",
         "@type": "@id"
       }
     }
@@ -357,113 +560,20 @@ Mastodon allows users to feature specific hashtags on their profile for easy bro
 }
 ```
 
-### Custom emojis {#emoji}
-
-Mastodon supports arbitrary emojis, that is, small images uploaded by admins and invokable via shortcodes. For this, an `Emoji` type is used. These emojis are listed in the `tag` property just like `Mention` and `Hashtag` objects, since they are entities that affect how the text is rendered. Example:
-
-```json
-{
-  "@context": [
-    "https://www.w3.org/ns/activitystreams",
-    {
-      "toot": "http://joinmastodon.org/ns#",
-      "Emoji": "toot:Emoji"
-    }
-  ],
-
-  "id": "https://example.com/@alice/hello-world",
-  "type": "Note",
-  "content": "Hello world :kappa:",
-  "tag": [
-    {
-      "id": "https://example.com/emoji/123",
-      "type": "Emoji",
-      "name": ":kappa:",
-      "icon": {
-        "type": "Image",
-        "mediaType": "image/png",
-        "url": "https://example.com/files/kappa.png"
-      }
-    }
-  ]
-}
-```
-
-### Focal points {#focalPoint}
-
-Mastodon supports setting a focal point on uploaded images, so that wherever that image is displayed, the focal point stays in view. This is implemented using an extra property `focalPoint` on `Image` objects. The property is an array of two floating points between -1.0 and 1.0, with 0,0 being the center of the image, the first value being x (-1.0 is the left edge, +1.0 is the right edge) and the second value being y (-1.0 is the bottom edge, +1.0 is the top edge). See [API Guidelines > Focal points]({{< relref "api/guidelines#focal-points" >}}) for more information. Example:
-
-```json
-{
-  "@context": [
-    "https://www.w3.org/ns/activitystreams",
-    {
-      "toot": "http://joinmastodon.org/ns#",
-      "focalPoint": {
-        "@container": "@list",
-        "@id": "toot:focalPoint"
-      }
-    }
-  ],
-
-  "id": "https://example.com/@alice/hello-world",
-  "type": "Note",
-  "content": "A picture attached!",
-  "attachment": [
-    {
-      "type": "Image",
-      "mediaType": "image/png",
-      "url": "https://example.com/files/cats.png",
-      "focalPoint": [
-        -0.55,
-        0.43
-      ]
-    }
-  ]
-}
-```
-
-{{< figure src="assets/focal-points.jpg" caption="A demonstration of various focal points and their coordinates." >}}
-
-The focal point of (-0.55, 0.43) in the example above corresponds to a point 55% to the left of center and 43% above center. This focal point should remain visible within the cropped thumbnail, if any cropping is done.
-
-### Blurhash {#blurhash}
-
-Mastodon generates colorful preview thumbnails for attachments. This is implemented using an extra property `blurhash` on `Image` objects. The property is a string generated by the [BlurHash algorithm](https://blurha.sh). Example:
-
-```json
-{
-  "@context": [
-    "https://www.w3.org/ns/activitystreams",
-    {
-      "toot": "http://joinmastodon.org/ns#",
-      "blurhash": "toot:blurhash"
-    }
-  ],
-
-  "id": "https://example.com/@alice/hello-world",
-  "type": "Note",
-  "content": "A picture attached!",
-  "attachment": [
-    {
-      "type": "Image",
-      "mediaType": "image/png",
-      "url": "https://example.com/files/cats.png",
-      "blurhash": "UBL_:rOpGG-oBUNG,qRj2so|=eE1w^n4S5NH"
-    }
-  ]
-}
-```
-
 ### Profile metadata {#PropertyValue}
 
-Mastodon supports arbitrary profile fields containing name-value pairs. This is implemented using the `attachment` property on actor objects, with objects in the array having a type of `PropertyValue` and a `value` property, both from the schema.org namespace. Example:
+Mastodon supports arbitrary profile fields containing name-value pairs. This is implemented using the `attachment` property on actor objects, with objects in the array having a type of `PropertyValue` and a `value` property, both from the schema.org namespace.
+
+{{<hint style="warning">}}
+As noted above while listing the [schema.org @context extensions](#schema), Mastodon currently incorrectly expects and maps the term `schema` to the base URI `http://schema.org#` instead of to the base URI `https://schema.org/`. Therefore, JSON-LD processors who use the correct context definition will fail to process profile fields correctly.
+{{</hint>}}
 
 ```json
 {
   "@context": [
     "https://www.w3.org/ns/activitystreams",
     {
+      "schema": "http://schema.org#",
       "PropertyValue": "schema:PropertyValue",
       "value": "schema:value"
     }
@@ -491,7 +601,7 @@ Mastodon supports arbitrary profile fields containing name-value pairs. This is
 This property is currently unused/deprecated due to the removal of Keybase support in Mastodon 3.5: <https://github.com/mastodon/mastodon/pull/17045>
 {{</hint>}}
 
-Mastodon supports integration with identity providers to prove that a profile is linked to a certain identity. This is implemented using the `attachment` property on actor objects, with objects in the array having a type of `IdentityProof` from the Mastodon namespace. The object also includes `signatureAlgorithm` and `signatureValue` from the W3ID Security Vocabulary namespace. Example:
+Mastodon supports integration with identity providers to prove that a profile is linked to a certain identity. This is implemented using the `attachment` property on actor objects, with objects in the array having a type of `IdentityProof` from the Mastodon namespace. The object also includes `signatureAlgorithm` and `signatureValue` from the W3ID Security Vocabulary namespace.
 
 ```json
 {
@@ -499,8 +609,7 @@ Mastodon supports integration with identity providers to prove that a profile is
     "https://www.w3.org/ns/activitystreams",
     "https://w3id.org/security/v1",
     {
-      "toot": "http://joinmastodon.org/ns#",
-      "IdentityProof": "toot:IdentityProof"
+      "IdentityProof": "http://joinmastodon.org/ns#IdentityProof"
     }
   ],
   "id": "https://mastodon.social/users/Gargron",
@@ -518,15 +627,14 @@ Mastodon supports integration with identity providers to prove that a profile is
 
 ### Discoverability flag {#discoverable}
 
-Mastodon allows users to opt-in or opt-out of discoverability features like the profile directory. This flag may also be used as an indicator of the user's preferences toward being included in external discovery services, such as search engines or other indexing tools. If you are implementing such a tool, it is recommended that you respect this property if it is present. This is implemented using an extra property `discoverable` on objects. Example:
+Mastodon allows users to opt-in or opt-out of discoverability features like the profile directory. This flag may also be used as an indicator of the user's preferences toward being included in external discovery services, such as search engines or other indexing tools. If you are implementing such a tool, it is recommended that you respect this property if it is present. This is implemented using an extra property `discoverable` on objects.
 
 ```json
 {
   "@context": [
     "https://www.w3.org/ns/activitystreams",
     {
-      "toot": "http://joinmastodon.org/ns#",
-      "discoverable": "toot:discoverable"
+      "discoverable": "http://joinmastodon.org/ns#discoverable"
     }
   ],
   "id": "https://mastodon.social/users/Gargron",
@@ -537,15 +645,14 @@ Mastodon allows users to opt-in or opt-out of discoverability features like the
 
 ### Suspended flag {#suspended}
 
-Mastodon reports whether a user was locally suspended, for better handling of these accounts. Suspended accounts in Mastodon return empty data. If a remote account is marked as suspended, it cannot be unsuspended locally. Suspended accounts can be targeted by activities such as Update, Undo, Reject, and Delete. This functionality is implemented using an extra property `suspended` on objects. Example:
+Mastodon reports whether a user was locally suspended, for better handling of these accounts. Suspended accounts in Mastodon return empty data. If a remote account is marked as suspended, it cannot be unsuspended locally. Suspended accounts can be targeted by activities such as Update, Undo, Reject, and Delete. This functionality is implemented using an extra property `suspended` on objects.
 
 ```json
 {
   "@context": [
     "https://www.w3.org/ns/activitystreams",
     {
-      "toot": "http://joinmastodon.org/ns#",
-      "suspended": "toot:suspended"
+      "suspended": "http://joinmastodon.org/ns#suspended"
     }
   ],
   "id": "https://example.com/@eve",
@@ -554,6 +661,133 @@ Mastodon reports whether a user was locally suspended, for better handling of th
 }
 ```
 
+### Hashtags {#Hashtag}
+
+Similar to the `Mention` subtype of Link already defined in ActivityStreams, Mastodon will use `Hashtag` as a subtype of Link in order to surface posts referencing some common topic identified by a string key. The Hashtag has a `name` containing the #hashtag microsyntax -- a `#` followed by a string sequence representing a topic. This is similar to the @mention microsyntax, where an `@` is followed by some string sequence representing a resource (where in Mastodon's case, this resource is expected to be an account). Mastodon will also normalize hashtags to be case-insensitive lowercase strings, performing ASCII folding and removing invalid characters.
+
+{{< caption-link url="https://github.com/mastodon/mastodon/blob/main/app/lib/hashtag_normalizer.rb" caption="app/lib/hashtag_normalizer.rb" >}}
+
+```json
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "Hashtag": "https://www.w3.org/ns/activitystreams#Hashtag"
+    }
+  ],
+  "id": "https://example.com/some-post",
+  "type": "Note",
+  "attributedTo": "https://example.com",
+  "content": "I love #cats",
+  "tag": [
+    {
+      "type": "Hashtag",
+      "name": "#cats",
+      "href": "https://example.com/tagged/cats"
+    }
+  ]
+}
+```
+
+### Custom emojis {#Emoji}
+
+Mastodon supports arbitrary emojis by including a `tag` of the `Emoji` type. Handling of custom emojis is similar to handling of mentions and hashtags, where the `name` of the tagged entity is found as a substring of the natural language properties (`name`, `summary`, `content`) and then linked to the local representation of some resource or topic. In the case of emoji shortcodes, the `name` is replaced by the HTML for an inline image represented by the `icon` property (where `icon.url` links to the image resource).
+
+```json
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "Emoji": "http://joinmastodon.org/ns#Emoji",
+    }
+  ],
+
+  "id": "https://example.com/@alice/hello-world",
+  "type": "Note",
+  "content": "Hello world :kappa:",
+  "tag": [
+    {
+      "id": "https://example.com/emoji/123",
+      "type": "Emoji",
+      "name": ":kappa:",
+      "icon": {
+        "type": "Image",
+        "mediaType": "image/png",
+        "url": "https://example.com/files/kappa.png"
+      }
+    }
+  ]
+}
+```
+
+### Focal points {#focalPoint}
+
+Mastodon supports setting a focal point on uploaded images, so that wherever that image is displayed, the focal point stays in view. This is implemented using an extra property `focalPoint` on `Image` objects. The property is an array of two floating points between -1.0 and 1.0, with 0,0 being the center of the image, the first value being x (-1.0 is the left edge, +1.0 is the right edge) and the second value being y (-1.0 is the bottom edge, +1.0 is the top edge). See [API Guidelines > Focal points]({{< relref "api/guidelines#focal-points" >}}) for more information.
+
+```json
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "focalPoint": {
+        "@container": "@list",
+        "@id": "http://joinmastodon.org/ns#focalPoint"
+      }
+    }
+  ],
+
+  "id": "https://example.com/@alice/hello-world",
+  "type": "Note",
+  "content": "A picture attached!",
+  "attachment": [
+    {
+      "type": "Image",
+      "mediaType": "image/png",
+      "url": "https://example.com/files/cats.png",
+      "focalPoint": [
+        -0.55,
+        0.43
+      ]
+    }
+  ]
+}
+```
+
+{{< figure src="/assets/focal-points.jpg" caption="A demonstration of various focal points and their coordinates." >}}
+
+The focal point of (-0.55, 0.43) in the example above corresponds to a point 55% to the left of center and 43% above center. This focal point should remain visible within the cropped thumbnail, if any cropping is done.
+
+### Blurhash {#blurhash}
+
+Mastodon generates colorful preview thumbnails for attachments. This is implemented using an extra property `blurhash` on `Image` objects. The property is a string generated by the [BlurHash algorithm](https://blurha.sh).
+
+```json
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "blurhash": "http://joinmastodon.org/ns#blurhash"
+    }
+  ],
+
+  "id": "https://example.com/@alice/hello-world",
+  "type": "Note",
+  "content": "A picture attached!",
+  "attachment": [
+    {
+      "type": "Image",
+      "mediaType": "image/png",
+      "url": "https://example.com/files/cats.png",
+      "blurhash": "UBL_:rOpGG-oBUNG,qRj2so|=eE1w^n4S5NH"
+    }
+  ]
+}
+```
+
+### Sensitive content {#sensitive}
+
+Mastodon uses the `as:sensitive` extension property to mark certain posts as sensitive. When a post is marked as sensitive, any media attached to it will be hidden by default, and if a `summary` is present, the status `content` will be collapsed behind this summary. In Mastodon, this is known as a **content warning**.
+
 ## Other functionality
 
 ### Secure mode {#secure-mode}
@@ -596,4 +830,4 @@ Signature: ... # a signature from an account on mastodon.social
     "https://mastodon.social/users/Gargron"
   ]
 }
-```
+```
\ No newline at end of file