OP3

OP3 — the Open Podcast Prefix Project — is John Spurlock's open-source answer to the closed black boxes most podcasters trust without inspection. Add the OP3 prefix to your RSS feed, and from that moment OP3 logs every download, calculates standard IAB-compliant metrics (downloads, uniques, geos, listening apps), and publishes everything to a free public stats page anyone can verify.

The entire codebase, deployment actions, and computation logic sit on GitHub, audit-ready. There's no IP-to-demographics enrichment from sketchy third parties, and the service runs on a single cloud platform with no data mixing.

As of late 2025 it measured over 18 million downloads monthly across 4,200+ shows. Where it shines is trust and transparency: if you've ever wondered whether your hosting analytics inflate numbers (or had it confirmed, as the iHeartMedia story revealed), OP3 is the independent verifier.

It's also genuinely free with no hidden tier wall. Where it falls short is at the enterprise sales table — OP3 isn't yet IAB-certified, so advertisers running formal RFPs may insist on Podtrac numbers in parallel.

There's also no demographic enrichment or attribution layer, just clean download data. Treat it as your verification baseline and source-of-truth, with another tool stacked on top for ad-buying scenarios where certification is required.