Many modern podcast hosts (like Buzzsprout, Megaphone, or Anchor/Spotify for Podcasters) support WebSub.
- When you publish an episode, your host sends a "ping" to a hub (like Google’s or a proprietary one).
- Spotify subscribes to these hubs. The moment the hub receives the ping, it notifies Spotify to come and fetch the updated feed immediately. This is why some episodes appear in minutes rather than hours.
3. XML Parsing and Hash Comparison
Once Spotify fetches the XML file, it parses the content to look for specific changes:
- GUID (Globally Unique Identifier): This is the most critical tag. Spotify looks at the for every . If it sees a GUID that doesn't exist in its database, it treats it as a new episode.
- PubDate: It checks the tag to determine the release order and whether a scheduled episode has become "live."
- Content Hashing: Spotify may also hash sections of the metadata. If the hash of an episode's description or title changes, it triggers an update to the display text in the app.