Referrer also important for this work

[jamescridland]

With Google Podcasts and Apple Podcasts appearing in-browser, my suspicion is that there's poor attribution for these products: particularly Google Podcasts. A user-agent pattern will merely show a browser for these services, rather than the correct attribution.

Looking at my own logs, "Referrer" is a helpful service here. I've spotted...

https://podcasts.google.com - Google Podcasts on the web
https://podcasts.apple.com/ca/podcast/* - Apple Podcasts
https://play.pocketcasts.com/web/new-releases - Pocket Casts' web interface
https://castbox.fm/episode/* - Castbox's web interface
https://player.fm* - Player FM
https://podknife.com* - Podknife

...there are others. Notable that Google Podcasts only gives their domain in the referrer, whereas Apple gives the full page URL (if your audio is also served through HTTPS). I'm unsure what would happen if audio is served in HTTP rather than HTTPS - many won't show any referrer at all.

A caution though - the referrer appears to be visible for app playback on Breaker, and also for Google Assistant's news service. So perhaps the referrer should only be checked once known Podcast useragents have been correctly parsed.

Just a thought to consider.