Podcast RSS Feeds
Contents
Trevor L Taylor hosts Hard Truths for a Soft World, and like most shows it reaches listeners through a file few of them ever see: a podcast RSS feed. The feed is a plain text document, written in a dialect of XML, that lists a show’s episodes and tells listening apps where to find each audio file. Understanding it explains why podcasting works the way it does, and why debates about the medium so often come back to openness.
What a feed contains
The industry newsletter Podnews offers a compact technical definition. Most podcasters would agree, it says, that a podcast is an audio file without copy protection1, available to download, distributed through an RSS feed using an enclosure tag. Each of those elements does work. The absence of copy protection means any app can play the file. Downloadability means it can be stored and heard offline. The feed and its enclosure are what make subscription automatic.
A feed has two layers. The channel describes the show as a whole: its title, a link, a description, artwork and categories. Under the channel sit items, one per episode, each with its own title, description, publication date and a unique identifier. The RSS 2.0 specification hosted at Harvard’s Berkman Center2 defines the enclosure as an optional part of an item with three required attributes: a URL saying where the file is located, a length in bytes, and a standard media type. For a podcast, that optional element is the whole point.
The other item fields matter more than they appear. The publication date tells apps which episode is newest and in what order to present the archive. The unique identifier, called a guid in the specification, lets an app recognize an episode it has already downloaded even if the title or description is edited later. When a publisher changes hosting companies, keeping those identifiers stable is what prevents every subscriber from receiving the whole back catalogue again as if it were new. Small mistakes in these fields are among the most common reasons a show appears out of order or duplicated in listening apps.
Directories layer their own requirements on top of the base format. Apple’s guidance for creators says that a show submitted from an RSS feed must meet technical requirements including required tags, at least one episode and artwork3, and that submission runs through an Apple Podcasts Connect account. Apple’s tags, written in their own namespace, became a de facto standard because so many listeners used its app.
Namespaces are how the format grows without breaking. RSS lets publishers add elements defined elsewhere, and older apps simply ignore tags they do not understand. The Podcast Index project maintains a newer podcast namespace4 with tags for transcripts, chapters, funding links, people, locations, seasons, trailers, alternate enclosures and more. A show can adopt any of them, and apps that support a tag gain a feature without anyone coordinating a central release.
The enclosure URL also matters for measurement. Because apps download the file from the address in the feed, the server holding that file is where downloads are counted. The IAB Tech Lab’s latest measurement guidance adds specific advice on prefix measurement and changes to RSS enclosure URLs5, since a moved file or a new analytics prefix changes what the server logs see. The entry on podcast audience measurement covers that process in detail.
The open ecosystem the feed creates
Because a feed is just a public file, nobody has to approve a show before it exists. A publisher can host audio anywhere, write a feed, and submit the feed address to as many directories and apps as it likes. Listeners can paste the same address into any app that reads RSS. Writing for Nieman Lab, Nicholas Quah described this as an open, decentralized publishing ecosystem6, valued for its dynamism and its low barrier to entry.
The same piece noted a complication: Apple, long a hands off steward, still exerted unique influence over collective decisions in the space simply because of its reach. Openness on paper, in other words, can coexist with practical dependence on a few large apps.
The open model also produces a rough census of the medium. Podnews explained that the Podcast Index is built mainly by discovering open podcast RSS feeds on the web7, and that it listed 3.8 million podcasts in early 2023, while the Apple catalogue was estimated at around 2.5 million. Anyone can download the index database and analyze it, which would be impossible in a closed system.
Feeds make it possible to change apps without losing a library. When Google decided to close Google Podcasts, YouTube said it would let users add podcast RSS feeds to their YouTube Music library8, including shows not hosted on YouTube, and would offer podcasters RSS uploads. Android Central reported that departing users could also download an OPML file of their subscriptions9 to import into another app. OPML is simply a list of feed addresses, and it works only because each show lives at a public address of its own.
Pressures on the open feed
The feed’s weakness is that it carries files rather than relationships. It cannot by itself verify who is listening, sell a subscription or count plays inside an app. Platforms that host audio themselves can do all of those things, and some have built features that never travel through RSS. Exclusive shows, paid tiers delivered through private feeds and video uploaded directly to a platform all sit partly outside the open system.
Dave Winer, the creator of RSS, put the risk bluntly in a post quoted by Sounds Profitable. The word podcast, he wrote, is coming to mean video interviews on YouTube10, and the only answer is to upgrade the open platform in ways that excite creators. The Podcast Index namespace is one such effort: it adds features such as transcripts and chapters to the feed itself, so that independent apps can compete with closed platforms on experience rather than only on principle.
For a publisher, the practical lesson is to treat the feed as the master copy of the show. Platforms come and go, as Google Podcasts did, but a feed at a stable address can be pointed at a new host, read by a new app or exported in a list of subscriptions. That is why the podcast RSS feed remains public infrastructure: a modest text file that keeps working long after the apps reading it have changed.
