What is Enclosure?
The enclosure tag is the critical RSS element that tells podcast apps where to download your audio file. It's what transforms a standard RSS feed into a podcast feed capable of delivering media content.
Enclosure Tag Anatomy
Every enclosure tag requires three attributes:
<enclosure
url="https://cdn.example.com/episodes/ep001.mp3"
length="48576000"
type="audio/mpeg"
/>
| Attribute | Purpose | Example |
|---|---|---|
url |
Direct link to audio file | https://cdn.example.com/ep001.mp3 |
length |
File size in bytes | 48576000 (≈46MB) |
type |
MIME type of the file | audio/mpeg for MP3 |
Common MIME Types
| Format | MIME Type | Usage |
|---|---|---|
| MP3 | audio/mpeg |
Most common, universal support |
| M4A/AAC | audio/x-m4a |
Apple devices, smaller files |
| OGG | audio/ogg |
Open source alternative |
Technical Requirements
URL requirements:
- Must be a direct link to the file (not a redirect chain)
- Should use HTTPS for security
- Must be publicly accessible (no authentication)
- Should be served from a CDN for reliability
File size accuracy:
The length attribute must match the actual file size in bytes. Incorrect values can cause:
- Download progress bars to display incorrectly
- Some apps to reject the episode entirely
- Streaming issues on certain players
Why MP3 dominates: While other formats exist, MP3 remains the standard because:
Why It Matters
The enclosure tag is quite literally what makes podcasting possible. If your RSS feed is the map, the enclosure is the treasure location—without it, apps have no way to download your audio.
Why enclosure correctness matters:
-
Download failures: A malformed enclosure URL means zero downloads for that episode. Apps simply can't find your audio.
-
Validation errors: Podcast directories reject feeds with invalid enclosures, potentially delisting your show.
-
Playback issues: Wrong file sizes cause streaming problems and inaccurate progress indicators.
-
Analytics accuracy: Since downloads are measured at the enclosure URL, incorrect URLs break your metrics.
Common enclosure problems:
| Issue | Symptom | Cause |
|---|---|---|
| 404 errors | Episode won't download | File moved or deleted |
| Wrong MIME type | Some apps won't play | Incorrect type attribute |
| Authentication required | Download fails silently | URL behind login |
| HTTP instead of HTTPS | Security warnings | Unencrypted URL |
Most podcast hosting platforms handle enclosure generation automatically, but understanding the tag helps you debug distribution issues when they arise.
How to Use This in Dispatch
Enclosure tags are automatically generated with verified accuracy when you upload episode audio:
Automatic handling:
- Correct URL pointing to our CDN
- Precise file size calculated from your upload
- Proper MIME type based on audio format
- HTTPS encryption for all URLs
What you don't need to worry about:
- File size calculations
- URL formatting
- MIME type detection
- CDN distribution
Replacing episode audio: If you upload a replacement audio file, the enclosure automatically updates with the new URL and file size. The GUID remains unchanged to prevent duplicate downloads.