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ActivityPub ​

A decentralized social networking protocol based upon the ActivityStreams 2.0 data format and JSON-LD. Pixelfed uses ActivityPub to send and recieve activities from other Pixelfed servers and other fediverse software like Mastodon.

Context ​

Click to expand status context example
json
"@context": [
    "https://w3id.org/security/v1",
    "https://www.w3.org/ns/activitystreams",
    {
        "Hashtag": "as:Hashtag",
        "sensitive": "as:sensitive",
        "schema": "http://schema.org/",
        "pixelfed": "http://pixelfed.org/ns#",
        "commentsEnabled": {
            "@id": "pixelfed:commentsEnabled",
            "@type": "schema:Boolean"
        },
        "capabilities": {
            "@id": "pixelfed:capabilities",
            "@container": "@set"
        },
        "announce": {
            "@id": "pixelfed:canAnnounce",
            "@type": "@id"
        },
        "like": {
            "@id": "pixelfed:canLike",
            "@type": "@id"
        },
        "reply": {
            "@id": "pixelfed:canReply",
            "@type": "@id"
        },
        "toot": "http://joinmastodon.org/ns#",
        "Emoji": "toot:Emoji",
        "blurhash": "toot:blurhash"
    }
]

Actors ​

Click to expand actor example
json
{
    "id": "https://example.org/users/dansup",
    "type": "Person",
    "following": "https://example.org/users/dansup/following",
    "followers": "https://example.org/users/dansup/followers",
    "inbox": "https://example.org/users/dansup/inbox",
    "outbox": "https://example.org/users/dansup/outbox",
    "preferredUsername": "dansup",
    "name": "dansup",
    "summary": "Example summary",
    "url": "https://example.org/dansup",
    "manuallyApprovesFollowers": false,
    "indexable": true,
    "publicKey": {
        "id": "https://example.org/users/dansup#main-key",
        "owner": "https://example.org/users/dansup",
        "publicKeyPem": "-----BEGIN PUBLIC KEY--..."
    },
    "icon": {
        "type": "Image",
        "mediaType": "image/jpeg",
        "url": "https://example.org/avatars/avatar.jpg"
    },
    "endpoints": {
        "sharedInbox": "https://example.org/f/inbox"
    },
    "alsoKnownAs": [
        "https://example.net/users/dansup"
    ]
}
Click to expand actor attributes
FieldTypeDescription
idStringID of the user
typeStringThe object type, always set to Person
followingStringThe following collection
followersStringThe followers collection
inboxStringThe inbox collection
outboxStringThe outbox collection
preferredUsernameStringThe account username
nameStringThe account display name
summaryStringThe account bio, may contain HTML
urlStringThe account url
manuallyApprovesFollowersBooleanIf the account is private, this value is set to true
indexableBooleanIf the account allows crawling, this value is set to true
publicKeyObjectThe public key data used for federation
iconObjectThe account avatar object
endpointsObjectThe sharedInbox will be set if configured
alsoKnownAsArrayA list of account aliases if applicable

Activities ​

Supported ActivityPub Activities

Click to expand Activities

Accept ​

object.type if Follow is transformed into a FollowRequest or Follow model.

Add ​

If type is Story then object object is transformed into Story model.

Announce ​

object object is transformed into a reblog_of_id Status model.

Create ​

Note and Question objects are transformed into statuses database models.

Delete ​

Person, Tombstone and Story objects with cached models are deleted.

Flag ​

Used for federated Reports.

Like ​

object object is transformed into a StatusLike model.

Reject ​

Used to reject or deny FollowRequest.

Story:Reaction ​

Transformed into StoryReaction model.

Story:Reply ​

Transformed into StoryReaction model.

Update ​

Used for ...

Undo ​

Used for ...

View ​

Transformed into StoryView model.

Collections ​

Following ​

The user following collection is comprised of accounts that this account follows. You may use the totalItems to get the following count for this account, it may return 0 if the account has opted to hide their following.

Click to expand following example
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/pixelfed/following",
    "type": "OrderedCollection",
    "totalItems": 2
}

Followers ​

The user followers collection is comprised of accounts that follow this account. You may use the totalItems to get the followers count for this account, it may return 0 if the account has opted to hide their followers.

Click to expand followers example
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/pixelfed/followers",
    "type": "OrderedCollection",
    "totalItems": 18189
}

Outbox ​

The user outbox collection is comprised of statuses authored by this account. You may use the totalItems to get the status count for this account, it may return 0 if the account is private.

Click to expand outbox example
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/pixelfed/outbox",
    "type": "OrderedCollection",
    "totalItems": 22
}

Objects ​

Accept ​

Accept.Follow ​

Approve/accept follow requests

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "type": "Accept",
    "id": "https://pixelfed.test/users/john#accepts/follows/2985",
    "actor": "https://pixelfed.test/users/john",
    "object": {
        "type": "Follow",
        "id": "https://other.test/35860bf0-9930-4131-b5b4-31d2f31df873",
        "actor": "https://other.test/users/jane",
        "object": "https://pixelfed.test/users/john"
    }
}

Announce ​

Announce (also known as boosting or re-tooting) a status to your followers

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/p/mike/631334127931904009/activity",
    "type": "Announce",
    "actor": "https://pixelfed.test/users/mike",
    "to": [
        "https://www.w3.org/ns/activitystreams#Public"
    ],
    "cc": [
        "https://pixelfed.test/users/mike",
        "https://pixelfed.test/users/mike/followers"
    ],
    "published": "2023-11-18T03:36:25+0000",
    "object": "https://pixelfed.test/p/dansup/630671772572999686"
}

Add ​

Add.Story ​

This object is used for federating new Stories, and uses Bearcaps. We currently deliver this activity to known Pixelfed instances only.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/stories/dansup/123456/activity",
    "type": "Add",
    "actor": "https://pixelfed.test/users/dansup",
    "to": [
        "https://pixelfed.test/users/dansup/followers"
    ],
    "object": {
        "id": "https://pixelfed.test/stories/dansup/123456",
        "type": "Story",
        "object": "bear:?t=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX&u=https://pixelfed.test/stories/dansup/123456"
    }
}

Create ​

Create.Note ​

Share a new status to your followers.

Click to expand
json
{
    "@context": [
        "https://w3id.org/security/v1",
        "https://www.w3.org/ns/activitystreams",
        {
            "Hashtag": "as:Hashtag",
            "sensitive": "as:sensitive",
            "schema": "http://schema.org/",
            "pixelfed": "http://pixelfed.org/ns#",
            "commentsEnabled": {
                "@id": "pixelfed:commentsEnabled",
                "@type": "schema:Boolean"
            },
            "capabilities": {
                "@id": "pixelfed:capabilities",
                "@container": "@set"
            },
            "announce": {
                "@id": "pixelfed:canAnnounce",
                "@type": "@id"
            },
            "like": {
                "@id": "pixelfed:canLike",
                "@type": "@id"
            },
            "reply": {
                "@id": "pixelfed:canReply",
                "@type": "@id"
            },
            "toot": "http://joinmastodon.org/ns#",
            "Emoji": "toot:Emoji",
            "blurhash": "toot:blurhash"
        }
    ],
    "id": "https://pixelfed.test/p/admin/1/activity",
    "type": "Create",
    "actor": "https://pixelfed.test/users/admin",
    "published": "2018-05-31T21:57:27+00:00",
    "to": [
        "https://www.w3.org/ns/activitystreams#Public"
    ],
    "cc": [
        "https://pixelfed.test/users/admin/followers"
    ],
    "object": {
        "id": "https://pixelfed.test/p/admin/1",
        "type": "Note",
        "summary": null,
        "content": "Hello Fediverse! <a href='https://pixelfed.test/discover/tags/pixelfed' class='mention hashtag status-link' rel='noopener'>#pixelfed</a> <a href='https://pixelfed.test/discover/tags/dogsOfPixelFed' class='mention hashtag status-link' rel='noopener'>#dogsOfPixelFed</a>",
        "inReplyTo": null,
        "published": "2018-05-31T21:57:27+00:00",
        "url": "https://pixelfed.test/p/admin/1",
        "attributedTo": "https://pixelfed.test/users/admin",
        "to": [
            "https://www.w3.org/ns/activitystreams#Public"
        ],
        "cc": [
            "https://pixelfed.test/users/admin/followers"
        ],
        "sensitive": false,
        "attachment": [
            {
                "type": "Image",
                "mediaType": "image/jpeg",
                "url": "https://pixelfed.test/storage/m/image.jpeg",
                "name": null
            }
        ],
        "tag": [
            {
                "type": "Hashtag",
                "href": "https://pixelfed.test/discover/tags/pixelfed",
                "name": "#pixelfed"
            },
            {
                "type": "Hashtag",
                "href": "https://pixelfed.test/discover/tags/dogsofpixelfed",
                "name": "#dogsOfPixelFed"
            }
        ],
        "commentsEnabled": true,
        "capabilities": {
            "announce": "https://www.w3.org/ns/activitystreams#Public",
            "like": "https://www.w3.org/ns/activitystreams#Public",
            "reply": "https://www.w3.org/ns/activitystreams#Public"
        },
        "location": null
    }
}

Delete ​

Delete.Note ​

Delete a status by the object id.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/p/admin/1#delete",
    "type": "Delete",
    "actor": "https://pixelfed.test/users/admin",
    "object": {
        "id": "https://pixelfed.test/p/admin/1",
        "type": "Tombstone"
    }
}

Delete.Story ​

Delete a story by the object id.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/stories/dansup/123456#delete",
    "type": "Delete",
    "actor": "https://pixelfed.test/users/dansup",
    "object": {
        "id": "https://pixelfed.test/stories/dansup/123456",
        "type": "Story"
    }
}

Follow ​

Follow a specific account as described by the object attribute.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "type": "Follow",
    "actor": "https://pixelfed.test/users/pixelfed",
    "object": "https://pixelfed.test/users/admin"
}

Like ​

Like a specific status as described by the object attribute.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/admin#likes/1",
    "type": "Like",
    "actor": "https://pixelfed.test/users/admin",
    "object": "https://pixelfed.test/p/admin/1"
}

Reject ​

Reject.Follow ​

Reject/deny a follow request by the actor.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "type": "Reject",
    "id": "https://pixelfed.test/users/example#rejects/follows/4284",
    "actor": "https://pixelfed.test/users/example",
    "object": {
        "type": "Follow",
        "id": "https://other.test/follows/9k2hoq7pj105mcdm",
        "actor": "https://other.test/users/john",
        "object": "https://pixelfed.test/users/example"
    }
}

Undo ​

Undo.Announce ​

Undo the announce/boost activity as described by the object.object attribute.

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/p/dansup/12345/undo",
    "actor": "https://pixelfed.test/users/dansup",
    "type": "Undo",
    "object": {
        "id": "https://pixelfed.test/p/dansup/12345/activity",
        "type": "Announce",
        "actor": "https://pixelfed.test/users/dansup",
        "to": [
            "https://www.w3.org/ns/activitystreams#Public"
        ],
        "cc": [
            "https://pixelfed.test/users/dansup",
            "https://pixelfed.test/users/dansup/followers"
        ],
        "published": "2018-09-10T00:03:25+0000",
        "object": "https://pixelfed.test/p/dansup/11767"
    }
}

Undo.Follow ​

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/pixelfed#follow/1/undo",
    "type": "Undo",
    "actor": "https://pixelfed.test/users/pixelfed",
    "object": {
        "id": "https://pixelfed.test/users/pixelfed#follows/1",
        "actor": "https://pixelfed.test/users/pixelfed",
        "object": "https://pixelfed.test/users/admin",
        "type": "Follow"
    }
}

Undo.Like ​

Click to expand
json
{
    "@context": "https://www.w3.org/ns/activitystreams",
    "id": "https://pixelfed.test/users/admin#likes/1/undo",
    "type": "Undo",
    "actor": "https://pixelfed.test/users/admin",
    "object": {
        "id": "https://pixelfed.test/users/admin#likes/1",
        "type": "Like",
        "actor": "https://pixelfed.test/users/admin",
        "object": "https://pixelfed.test/p/admin/1"
    }
}

Update ​

Update.Note ​

Click to expand
json
{
    "@context": [
        "https://w3id.org/security/v1",
        "https://www.w3.org/ns/activitystreams",
        {
            "Hashtag": "as:Hashtag",
            "sensitive": "as:sensitive",
            "schema": "http://schema.org/",
            "pixelfed": "http://pixelfed.org/ns#",
            "commentsEnabled": {
                "@id": "pixelfed:commentsEnabled",
                "@type": "schema:Boolean"
            },
            "capabilities": {
                "@id": "pixelfed:capabilities",
                "@container": "@set"
            },
            "announce": {
                "@id": "pixelfed:canAnnounce",
                "@type": "@id"
            },
            "like": {
                "@id": "pixelfed:canLike",
                "@type": "@id"
            },
            "reply": {
                "@id": "pixelfed:canReply",
                "@type": "@id"
            },
            "toot": "http://joinmastodon.org/ns#",
            "Emoji": "toot:Emoji"
        }
    ],
    "id": "https://pixelfed.test/p/dansup/567257798031955417#updates/4269",
    "type": "Update",
    "actor": "https://pixelfed.test/users/dansup",
    "published": "2023-05-26T21:01:10+00:00",
    "to": [
        "https://www.w3.org/ns/activitystreams#Public"
    ],
    "cc": [
        "https://pixelfed.test/users/dansup/followers",
        "https://example.net/users/pixelfed"
    ],
    "object": {
        "id": "https://pixelfed.test/p/dansup/567257798031955417",
        "type": "Note",
        "summary": null,
        "content": "Don't mind me, just testing post editing on <a class=\"u-url list-slug\" href=\"https://pixelfed.test/@pixelfed@example.net\" rel=\"external nofollow noopener\" target=\"_blank\">@pixelfed@example.net</a> \ud83d\ude09<br />\n<br />\nEdit: It works!!",
        "inReplyTo": null,
        "published": "2023-05-25T01:59:58+00:00",
        "url": "https://pixelfed.test/p/dansup/567257798031955417",
        "attributedTo": "https://pixelfed.test/users/dansup",
        "to": [
            "https://www.w3.org/ns/activitystreams#Public"
        ],
        "cc": [
            "https://pixelfed.test/users/dansup/followers",
            "https://example.net/users/pixelfed"
        ],
        "sensitive": false,
        "attachment": [
            {
                "type": "Image",
                "mediaType": "image/jpeg",
                "url": "https://example.org/m/1.jpg",
                "name": "Night sky"
            },
            {
                "type": "Image",
                "mediaType": "image/jpeg",
                "url": "https://example.org/m/2.jpg",
                "name": "Sunrise at dawn"
            }
        ],
        "tag": [
            {
                "type": "Mention",
                "href": "https://example.net/users/pixelfed",
                "name": "@pixelfed@example.net"
            }
        ],
        "commentsEnabled": true,
        "updated": "2023-05-26T21:01:10+00:00",
        "capabilities": {
            "announce": "https://www.w3.org/ns/activitystreams#Public",
            "like": "https://www.w3.org/ns/activitystreams#Public",
            "reply": "https://www.w3.org/ns/activitystreams#Public"
        },
        "location": null
    }
}

Update.Person ​

Click to expand
json
{
    "@context": [
        "https://w3id.org/security/v1",
        "https://www.w3.org/ns/activitystreams",
        {
            "pixelfed": "http://pixelfed.org/ns#",
            "manuallyApprovesFollowers": "as:manuallyApprovesFollowers",
            "alsoKnownAs": {
                "@id": "as:alsoKnownAs",
                "@type": "@id"
            },
            "movedTo": {
                "@id": "as:movedTo",
                "@type": "@id"
            },
            "indexable": "pixelfed:indexable"
        }
    ],
    "id": "https://pixelfed.test/users/admin#updates/1704185077",
    "actor": "https://pixelfed.test/users/admin",
    "type": "Update",
    "object": {
        "id": "https://pixelfed.test/users/admin",
        "type": "Person",
        "following": "https://pixelfed.test/users/admin/following",
        "followers": "https://pixelfed.test/users/admin/followers",
        "inbox": "https://pixelfed.test/users/admin/inbox",
        "outbox": "https://pixelfed.test/users/admin/outbox",
        "preferredUsername": "admin",
        "name": "Admin",
        "summary": "pixelfed.social Admin. Managed by @dansup",
        "url": "https://pixelfed.test/admin",
        "manuallyApprovesFollowers": false,
        "indexable": false,
        "publicKey": {
            "id": "https://pixelfed.test/users/admin#main-key",
            "owner": "https://pixelfed.test/users/admin",
            "publicKeyPem": "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwrugl5+u144q5Lkpfajl\ntx32cSFxYoA0BpMCEThiq195kpMw3h7kAUIOatI9IpoXb70mQr27l1L7kMXoj3nQ\nGy1EvIpZ/8tjH6cGxh65Ld+PXI42qyjyHeGRXWpfKqVxiB3ip9gtDQyWSAjVbt33\nfjJcMXFQXxUeX8eUZ/EJ/6hlK7okfzP55w1UGBfrQETCmf7P2egqM1dCbx7cfZdJ\n4dcGULEAxwYSTtfmUTih/djT5oE7kif8GIr9pdMuobiHrI6BP/ELwFU9t3nIQhjv\nfYGS/I5qIMeF/hvZDcak3aXXejcAwF8MJSiqDJtWeB2t8+xi8HsfMm5NbSmFv6o5\nBwIDAQAB\n-----END PUBLIC KEY-----\n"
        },
        "icon": {
            "type": "Image",
            "mediaType": "image/jpeg",
            "url": "https://pixelfed.test/storage/avatars/avatar.png"
        },
        "endpoints": {
            "sharedInbox": "https://pixelfed.test/f/inbox"
        }
    }
}

Extensions ​

Blurhash ​

Pixelfed supports the blurhash algorithm to generate efficient image previews to show as a placeholder while content is loading, or for sensitive statuses.

Click to expand blurhash example
json
{
    "@context": [
        "https://www.w3.org/ns/activitystreams",
        {
            "toot": "http://joinmastodon.org/ns#",
            "blurhash": "toot:blurhash"
        }
    ],

    "id": "https://pixelfed.test/p/dansup/618893826647911311",
    "type": "Note",
    "content": "Happy #caturday!",
    "attachment": [
        {
            "type": "Image",
            "mediaType": "image/jpeg",
            "url": "https://example.org/media/caturday.jpg",
            "blurhash": "UEE:0k_2oexa~pIVtRM{oH%L?bM{9F4nWB~W", 
        }
    ]
}

Capabilities (Comment Controls) ​

Pixelfed supports basic comment controls, allowing users to disable Announce, Like and reply activities. The announce, like and reply attributes will be either NULL or https://www.w3.org/ns/activitystreams#Public to represent basic ACL.

Click to expand capabilities example
json
{
    "@context": [
        "https://www.w3.org/ns/activitystreams",
        {
            "pixelfed": "http://pixelfed.org/ns#",
            "commentsEnabled": {
                "@id": "pixelfed:commentsEnabled",
                "@type": "schema:Boolean"
            },
            "capabilities": {
                "@id": "pixelfed:capabilities",
                "@container": "@set"
            },
            "announce": {
                "@id": "pixelfed:canAnnounce",
                "@type": "@id"
            },
            "like": {
                "@id": "pixelfed:canLike",
                "@type": "@id"
            },
            "reply": {
                "@id": "pixelfed:canReply",
                "@type": "@id"
            },
        }
    ],
    "id": "https://pixelfed.test/p/dansup/618893826647911311",
    "type": "Note",
    "content": "Happy #caturday!",
    "capabilities": {
        "announce": "https://www.w3.org/ns/activitystreams#Public", 
        "like": "https://www.w3.org/ns/activitystreams#Public", 
        "reply": "https://www.w3.org/ns/activitystreams#Public"
    },
}

Content Warnings ​

Pixelfed employs the as:sensitive extension property, similar to Mastodon, for indicating sensitive content in posts. When this property is applied to a post in Pixelfed, any associated media will be concealed by default. Additionally, if the post includes a summary, the main content of the post will be collapsed behind this summary, functioning as a content warning. This feature ensures that sensitive material is not immediately visible to viewers, requiring an action to view it.

Click to expand content warnings example
json
{
    "@context": [
        "https://www.w3.org/ns/activitystreams",
        {
            "sensitive": "as:sensitive", 
        }
    ],
    "id": "https://pixelfed.test/p/dansup/618893826647911311",
    "type": "Note",
    "summary": null,
    "content": "Happy #caturday!",
    "sensitive": false
}

Custom Emoji ​

Pixelfed, akin to Mastodon, accommodates custom emojis through the integration of an Emoji type tag. This feature operates similarly to the handling of mentions and hashtags.

In this system, the custom emoji is recognized as a substring within the natural language elements (such as the name, summary, or content) of a post. This substring, representing the emoji's shortcode, is then dynamically linked to its corresponding visual representation. Specifically, the shortcode name is substituted in the post with the HTML code for an inline image, which is derived from the icon property of the emoji. The icon's URL directly links to the image resource, ensuring that the custom emoji is properly displayed within the content.

Click to expand custom emoji example
json
{
    "@context": [
        "https://www.w3.org/ns/activitystreams",
        {
            "toot": "http://joinmastodon.org/ns#",
            "Emoji": "toot:Emoji", 
        }
    ],

    "id": "https://pixelfed.test/p/dansup/647727972628135937",
    "type": "Note",
    "content": "test :pixelfed: custom emoji", 
    "tag": [
        {
            "id": "https://pixelfed.test/emojis/12",
            "type": "Emoji",
            "name": ":pixelfed:", 
            "updated": "2022-01-21T02:01:03+00:00",
            "icon": {
                "type": "Image",
                "mediaType": "image/png",
                "url": "https://pixelfed.test/storage/emoji/12.png"
            }
        }
    ]
}

Location (Geo-tagging) ​

Pixelfed supports location geo-tagging statuses by selecting a location from a shared dataset. The location object contains a type attribute which is always Place, a name attribute of the location city, the longitude and latitude attributes describe the geographic location and finally the country attribute is the location country.

Click to expand location example
json
{
    "@context": [
        "https://www.w3.org/ns/activitystreams",
    ],
    "id": "https://pixelfed.test/p/dansup/75783646421848064",
    "type": "Note",
    "summary": null,
    "content": "Menlo Park, aka Pixelfed Park",
    "location": { 
        "type": "Place", 
        "name": "Menlo Park", 
        "longitude": "-122.182190", 
        "latitude": "37.453830", 
        "country": "USA"
    } 
}

Authorized Fetch ​

Pixelfed, like other platforms in the Fediverse including Mastodon, uses digital signatures to ensure secure and authenticated federation requests. This compatibility with Mastodon's Authorized Fetch protocol is a crucial aspect of maintaining a secure and interoperable federated network.

Click to learn more

Here's how Pixelfed signs federation requests to align with Mastodon's Authorized Fetch mechanism:

  1. HTTP Signatures: Pixelfed employs HTTP Signatures to sign federation requests. This is a standard method used across the Fediverse for authenticating HTTP requests, ensuring that the request is sent by a known and verified entity.

  2. Digital Signature Creation: When Pixelfed sends a federation request (like a post or an activity), it generates a digital signature using the private key of the sending user or server. This signature is unique to each request and is based on the content of the HTTP request.

  3. Including Public Key Information: Pixelfed includes information in its federation requests about how to find the public key needed to verify the signature. This is usually a URL pointing to an actor's profile where the public key can be fetched.

  4. Verification on the Receiving End: When Mastodon, or any other compatible platform in the Fediverse, receives a request from Pixelfed, it uses the provided information to fetch the public key and verify the signature. This process ensures that the request is indeed from the claimed source and has not been tampered with during transmission.

  5. Timestamps and Replay Prevention: To prevent replay attacks, Pixelfed includes timestamps in its signed requests. Mastodon and other platforms check these timestamps to ensure that the request is recent and not a replay of an old request.

  6. Compliance with ActivityPub Protocol: Both Pixelfed and Mastodon adhere to the ActivityPub protocol, which standardizes the way federated services communicate. The use of HTTP Signatures for authentication is a part of this protocol.

  7. Authorized Fetch Compatibility: For Mastodon's Authorized Fetch, when Pixelfed sends a request to Mastodon (like accessing a post or user data), Mastodon checks the signature to authenticate the request. Only if the signature is valid and the request is authorized, Mastodon will fulfill the request, aligning with its privacy and security standards.

By following these steps, Pixelfed ensures that its federation requests to Mastodon and other Fediverse platforms are secure, authenticated, and in line with the privacy standards set by these platforms. This method effectively maintains user privacy and data integrity across different services in the federated network.