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The New iTunes Podcast RSS Tags

Posted by Padraig on Jun 13, 2017

Last Friday, Apple announced some additional XML tags that it will support in podcast RSS feeds. Here’s the video of the session where the tags were announced and here’s a PDF explaining each tag.

First, lets give Apple some credit — these features could have been built into their Podcast Connect backend, which would have brought podcasting further under its control. Apple instead chose to extend open RSS feeds. This is an encouraging signal for third party podcast app makers and for anyone else who cares about the openness of the podcasting ecosystem.

News Podcasts and Story Podcasts

The majority of podcasts can be categorized as news-type shows. Some clear examples of this are Pod Save America’s political analysis, The Talk Show’s Apple discussions and Football Weekly’s soccer coverage. Listeners of these shows are not expected to know the context provided by previous episodes, and the most recent episode is the most relevant. Apple refers to these as “episodic” which is ambiguous, but I’m going to stick to their terminology for the rest of this post.

There is another type that is less common but still important: story-type shows. Some of the most successful podcasts in the last few years have been story-type shows, which are much more like a TV series than a news show. Serial and S-Town are the obvious examples. Listeners of these shows are expected to listen in order, starting from the first episode. Apple calls these “serial” podcasts.

Every podcast app I’ve tried treats every podcast like an episodic one. When you first subscribe, episodes that are older than the most recent one are marked as played. They’re not actually played, but this shortcut taken by app makers has persisted for years and is now a part of how podcast apps are expected to work. Castro is strict about the meaning of “played”, so older episodes go in the archive instead of being marked as played but the effect here is the same; older episodes are de-emphasized. The one token gesture towards serial shows in Castro is on the subscribe screen, Castro shows the oldest and newest episodes for easy queuing if you do intend to listen from the start. This helps, but it doesn’t add up to solid serial podcast support.

One of the challenges for podcast apps in accommodating serial shows is that there’s no way for podcasters to signal that their show is meant to be listened sequentially. App makers could build a serial workflow but it would require every user to understand what that is and then each user would have to toggle a setting for each relevant subscription. Users rarely change default settings so its unlikely that this feature would be used even where appropriate.

What do the new tags do?

These new tags provide a means for podcasters to indicate directly in the feed that a podcast is an episodic podcast or a serial podcast. This gives podcast app makers all the information they need to handle these shows correctly without user intervention.

Additionally these tags allow podcasters to explicitly assign season numbers and episode numbers, and to distinguish bonus or trailer episodes from full episodes.

With this information, apps will be able to:

  • pick the correct starting point when a user subscribes to a serial podcast.
  • provide appropriate auto-queue behaviour for serial podcasts.
  • highlight and play trailer episodes for users who are browsing to help them decide if they want to subscribe.

The new tags in practice

What about other podcast types?

There’s a third type of podcast that is not well served by either the episodic or the serial approach. A good example is In Our Time which is made up of hundreds of interviews with experts on various historical people and events. The relevant factor for deciding whether to listen is the episode’s topic. An episode from 5 years ago may be more relevant to your interests than one published today. It’s a shame that podcast apps bury these older episodes. Perhaps there is an opportunity to add a third type that identifies these shows separately?

Should bonus episodes get season/episode numbers?

While integrating the parsing of these tags to our server, I picked one serial podcast feed (Serial) and manually added the tags myself. A number of questions arose about how to use the tags:

  • The Serial podcast feed includes three episodes during season two that don’t progress the season story, but instead provide updates on the events of season one. Of the three possible episode types (full, bonus, trailer). It makes sense to me to consider these to be bonus episodes.
  • The three bonus episodes have a preferred order for playback, so it also makes sense that they should have episode numbers.
  • Which season should they belong to? They relate to season one content, but were published during season two. Should they be their own season?
  • If they’re in season one or two, what are their episode numbers?

Update: I filed rdar://33007101 about this

How should trailers be handled?

  • The feed also contains a preview and a trailer for a different podcast called S-Town. These should reasonably be classified as trailers, but they’re not trailers for the current show. If a podcast app assumes that a trailer episode provides a preview of the show in question, it’ll be playing the S-Town trailer on the Serial podcast.
  • Should trailers have season numbers?
  • How should a podcast app handle multiple trailers in a feed?

There are a range of acceptable answers to these questions but the point is that podcasters will need to think through these decisions carefully because their choices will affect the display of their episodes. If there’s too much ambiguity, it’ll be hard for podcast apps to do the right thing in all cases. Over the next few years I expect that some best-practises will evolve.

Update: I filed rdar://33006962 about this


It became clear to me even when considering Serial, which is perhaps, the canonical example of a serial podcast feed, that there were a number of questions about how best to choose values for these new tags.

Podcasters should start thinking about answering these questions and adding these tags to their feeds right away. Even episodic podcasts will benefit from the episodeTypes and explicit episode numbers. This will allow app makers to start building features that take advantage of them and understanding any unexpected usage.

I finished integrating the new tags into our aggregator yesterday, and it has already found a podcast that uses them: The Incomparable’s “This Week in Time Travel” uses the new episode number, title and episodeType tags. Well done Incomparable people. 1 down, 399,999 more podcasts to go!

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