Substack RSS Feed Fetcher

An HTTP GET endpoint that fetches full RSS files from a list of Substack publications.

Features

✅ Fetches full RSS content from Substack feeds
✅ Supports multiple feeds in a single request
✅ Concurrent fetching for better performance
✅ Error handling with detailed feedback
✅ Flexible input methods (query parameters or hardcoded defaults)
✅ Returns structured JSON with metadata

Usage

Default Behavior

By default, the endpoint fetches the hardcoded example feed:

GET /

Returns RSS content from https://jtbx.substack.com/feed

Custom Feeds via Query Parameters

You can specify custom feeds using the feeds query parameter:

Comma-separated URLs:

GET /?feeds=https://jtbx.substack.com/feed,https://stratechery.substack.com/feed

JSON array format:

GET /?feeds=["https://jtbx.substack.com/feed","https://stratechery.substack.com/feed"]

Response Format

The endpoint returns a JSON response with the following structure:

{
  "success": true,
  "feeds": [
    {
      "url": "https://jtbx.substack.com/feed",
      "content": "<?xml version=\"1.0\" encoding=\"UTF-8\"?>...",
      "fetchedAt": "2025-05-31T18:49:29.163Z",
      "success": true
    }
  ],
  "errors": [],
  "totalRequested": 1,
  "totalSuccessful": 1,
  "totalFailed": 0,
  "fetchedAt": "2025-05-31T18:49:29.163Z"
}

Response Fields

success: Overall success status
feeds: Array of successfully fetched feeds
- url: The RSS feed URL
- content: Full RSS XML content
- fetchedAt: Timestamp when the feed was fetched
- success: Individual feed success status
errors: Array of failed feeds with error details
totalRequested: Total number of feeds requested
totalSuccessful: Number of successfully fetched feeds
totalFailed: Number of failed feeds
fetchedAt: Overall request timestamp

Error Handling

The endpoint gracefully handles various error scenarios:

Invalid URLs: Returns 400 with error details
Network failures: Individual feed failures are captured in the errors array
Invalid query parameters: Returns 400 with usage examples

Error Response Example

{
  "success": false,
  "error": "Invalid URL: not-a-valid-url",
  "timestamp": "2025-05-31T18:49:29.163Z"
}

Examples

Single Feed

curl "https://your-endpoint.com/?feeds=https://jtbx.substack.com/feed"

Multiple Feeds

curl "https://your-endpoint.com/?feeds=https://jtbx.substack.com/feed,https://stratechery.substack.com/feed"

JSON Array Format

curl "https://your-endpoint.com/?feeds=[\"https://jtbx.substack.com/feed\",\"https://stratechery.substack.com/feed\"]"

Technical Details

Built with TypeScript for Val Town
Uses concurrent fetching with Promise.all() for performance
Validates URLs before making requests
Returns full RSS XML content (not parsed)
Includes comprehensive error handling and logging
CORS enabled for browser usage

Use Cases

RSS feed aggregation
Content monitoring and analysis
Building custom RSS readers
Data collection for research
Newsletter content backup

Rate Limiting

The endpoint respects standard HTTP rate limiting. For high-volume usage, consider implementing caching or batching strategies.

ashryanio

fetchRssForSubcurrent