Download Calculation

"Downloads" are currently the industry-standard way of measuring a podcast's audience, they are visible evidence on the server-side (hosting companies and analytics prefixes) without the need for any coordination or special APIs from every podcast player app.

Of course, many podcast apps auto-download episodes, so a Download does not necessarily equal a Listen. Learn more about podcast stats.

Over time, podcast hosting companies and advertising standards entities such as the IAB have developed best practices about turning raw server logs into unique listener requests.

As part of OP3's commitment to auditable infrastructure, our download calculation is described below, with links to any relevant codepaths.

How does OP3 calculate Downloads?

OP3 sees incoming HTTP requests for podcast episode media files as soon as podcasters add our prefix to podcast episodes in their feed.

All incoming requests are quickly redirected to their destination with a 302 and logged, but not all requests become Downloads:

• First, we ignore all non-GET requests.
• We ignore all range requests that don't ask for more than two bytes, except bytes=0-1 requests (see A Tale of Two Bytes for rationale).
• Duplicate requests in the same UTC day (24 hours) based on the secure IP address hash + User-Agent + Referer for the same normalized episode url are ignored.
• Using the User-Agent header and user-agents-v2, we ignore:
  • Requests with no User-Agent header
  • A known user agent of type 'bot'
  • A known user agent of type 'library' with a category of 'bot'
  • An unknown user agent including the text 'bot', 'crawler', or 'spider'
  • One other uncommon case found in the wild (using OP3 data)
  • Web apps observed to preload audio before user playback

Downloads are associated to a podcast by matching the normalized url (removing tracking prefixes and client-added params) to an enclosure or alternate enclosure found in a public podcast feed.