Online Tool Store
· 4 min read
How to Check a Podcast Feed Before Submitting
Heshan Fernando
Co-founder & COO
Episode 14 goes out and every subscriber’s app shows episodes 1 through 13 as new, unplayed, and at the top of their queue.
The publishing tool regenerated the GUIDs. Nothing can undo it, because apps have already recorded the new identifiers as new episodes.
GUIDs are the thing to get right first
A GUID is the unique identifier for an episode. Podcast apps use it, and only it, to decide whether an item in the feed is one they have seen before.
That produces two failure modes, both unrecoverable:
A changed GUID makes an existing episode appear as new. Subscribers get a notification, it moves to the top of their list, and download counts for it start again. Do this to a back catalogue and every subscriber gets your entire archive at once.
A duplicated GUID makes two episodes look like one. Apps show whichever they saw first, and the other is invisible — permanently, for anyone already subscribed.
The rule is that a GUID is assigned once and never changes, regardless of what happens to the episode’s title, description, URL or audio file. Most hosting platforms handle this correctly; feeds generated by hand or by a general-purpose CMS frequently do not.
| Change | Safe? |
|---|---|
| Edit title or description | Yes |
| Replace audio file | Yes, if GUID unchanged |
| Change episode URL | Yes, if GUID unchanged |
| Change GUID | No — appears as new |
Artwork requirements are strict and simple
Directories specify artwork dimensions, and undersized artwork is a common rejection reason that takes minutes to fix.
The general requirements: square, at least 1400 × 1400 pixels, with 3000 × 3000 recommended, in JPEG or PNG, under a maximum file size, and served over HTTPS at a URL that does not redirect.
Two details that catch people: artwork must be square, and a redirect on the artwork URL causes failures in some directories even though the image is reachable.
Text on artwork should be legible at thumbnail size, since that is how most people will see it. Show detail is wasted; the show name and a strong shape are what read at 100 pixels.
Enclosure details matter more than they look
The enclosure element points at the audio file and carries a length and a type.
Length should be the file size in bytes. Some clients use it for progress display and buffering, and a wrong or missing value produces odd playback behaviour — scrubbing that jumps, or a progress bar that does not match the audio.
Type must match the actual file. An MP3 declared as audio/mpeg is correct; declared as something else it may not play in some clients.
The URL must be a direct link to the file, served over HTTPS, and stable. Changing an episode’s audio URL is fine as long as the GUID does not change with it.
Validate before submitting, not after
Directories cache feeds. A problem fixed after submission can take days to propagate, and a rejected submission sometimes requires resubmitting and waiting again.
The checks worth running before the first submission: required channel tags present, every episode has a unique stable GUID, artwork meets the dimensions, every enclosure has a correct length and type, and the feed is valid XML served with the right content type.
Ten minutes before submission saves several days of waiting afterwards.
Common mistakes to avoid
- Regenerating GUIDs when migrating hosts, which republishes the whole catalogue.
- Non-square or undersized artwork.
- A redirect on the artwork or enclosure URL.
- Missing or wrong enclosure length.
- Submitting before validating, then waiting days for a cache to clear.
How to do it with Podcast RSS Feed Validator
The Podcast RSS Feed Validator checks the feed in your browser.
- Paste the feed XML or its URL.
- Fix errors before warnings — a missing required tag means rejection.
- Check GUIDs specifically for uniqueness and stability.
- Validate before the first submission, and again after any host migration.
Other developer tools are in the tools directory.
Frequently asked questions
Why do GUIDs matter so much?
Because apps identify episodes by GUID alone. Change one and the episode reappears as new for every subscriber; duplicate one and an episode becomes invisible. Neither is fixable after the fact.
What artwork size is needed?
Square, at least 1400 pixels, with 3000 recommended, served over HTTPS without a redirect. Undersized artwork is a common rejection reason and trivial to fix beforehand.
Does the enclosure length matter?
Yes. It should be the file size in bytes. Some clients use it for progress and buffering, and a wrong value produces scrubbing and progress bar problems.
Final thought
Check the GUIDs before anything else, especially when changing hosts. It is the one error you cannot take back once subscribers have the feed.