Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

🎙 Pubcast

Gitter chat

An experimental (Read: not-usable or in anyway done) distributed/federated podcasting platform based on ActivityPub.


Getting started:

Ensure that you're using go11 with go-modules turned on.

export GO111MODULE=on # Put this in your .zshrc or .bash_profile or whatnot

Clone/Download the project with:

go get

Building a binary with make (or mmake if you're fancy):


Building and then running that binary:

make run

Running tests:

make test

Setting up your database (this works best if you have postgres already running locally):

make database

Creating a new migration in db/migrations:

make migration NAME=some_name_here

Learning about ActivityPub


Basic Description

ActivityPub gives every user (or actor in it's vocab) on a server an "inbox" and an "outbox". But these are really just endpoints:

ActivityPub asks that you accept GET and POST requests to these endpoints where a POST tells a the server to put that in a user's queue or feed and GET lets the user retrieve info from the feed.

You send messages called ActivityStreams that are really just a special spec of JSON:

{"@context": "",
 "type": "Create",
 "id": "https://social.example/alyssa/posts/a29a6843-9feb-4c74-a7f7-081b9c9201d3",
 "to": ["https://chatty.example/ben/"],
 "author": "https://social.example/alyssa/",
 "object": {"type": "Note",
            "id": "https://social.example/alyssa/posts/49e2d03d-b53a-4c4c-a95c-94a6abf45a19",
            "attributedTo": "https://social.example/alyssa/",
            "to": ["https://chatty.example/ben/"],
            "content": "Say, did you finish reading that book I lent you?"}

Objects, Actors, and Activities

(Note: Pubcast uses a slightly different internal naming than ActivityPub. To have more understandable code in the context of podcasts, ActivityPub's Organization actor type is a Show inside Pubcast. Additionally, the Object type is a Pubcast Episode.)

ActivityPub is based on a formalized vocabulary of data types, actions and folks doing the actions.

An Object is a generic data type written in JSON:

  "@context": "",
  "type": "Object",
  "id": "http://www.test.example/object/1",
  "name": "A Simple, non-specific object"

Objects have a set collection of formalized properties such as id, name, url, etc but you technically can create your own. Objects serve as a base type for other Activity Steam's core set of types.

For example, there are a set of actor types that themselves are Objects.

/* A "Person" actor type */
  "@context": "",
  "type": "Person",
  "name": "Sally Smith"

Activities are also subtypes of Object, and are used to describe relationships between objects. Some examples of activities include:

  • Accept
  • Create
  • Move
  • Question
  • Undo
  • Follow
  • View

An Activity json might look something like this:

  "@context": "",
  "summary": "Sally created a note",
  "type": "Create",
  "actor": {
    "type": "Person",
    "name": "Sally"
  "object": {
    "type": "Note",
    "name": "A Simple Note",
    "content": "This is a simple note"



Podcast Object

Podcasts include four main pieces of information: the header info, the shownotes, the preview, and the audio. A Header includes the title and date of the show. Shownotes are a collection of info about the show; they're basically an HTML supported description. A preview is an image thumbnail for the show. Audio is the actual stuff you're listening to.

A Podcast ActivityStream Object can therefore look something like this:

"object" : {
 "id": "",
 "type": "Podcast",
 "name": "This American Life",
 "date": "2008-09-15T15:53:00",
 "shownotes": "Check out our <a href=''>website!</a>",
 "preview": {
    "type": "Image",
    "href": "áiréad.jpg",
    "mediaType": "image/jpeg"
  "audio": {
    "type": "Audio",
    "href": "",
    "mediaType": "audio/mp4"