Apple Podcasts HLS streams: how they work
Apple Podcasts announced enhanced support for video, coming with iOS 26.4.
So, how does the Apple Podcasts HLS video feature technically work? Strap in…
Apple hasn’t published the specific requirements for HLS video within Apple Podcasts; it’s proprietary information, covered by an NDA (though we’re hopeful that it might be more public once it launches). But, here’s what we’ve learnt so far:
The basics
Apple Podcasts video uses Apple’s own HLS specification - RFC8216 - for on-demand streaming, and their authoring specification for Apple devices is the most important. The .m3u8 master playlist file is delivered to Apple through the API that partner podcast hosts also use for Apple Podcasts subscriptions and show submission.
Partners deliver a multivariant playlist - a master playlist that defines different versions of the video and audio.
From launch partners, there appear only to be videos from ART19 and Acast inside Apple Podcasts at the moment (and one access-gated show that’s Apple’s own). Both of those are using AAC-LC for their audio (the base AAC format), and H.264 for their video.
The videos
Apple’s default bitrate specifications, for iOS, suggest 2000 kbps for wifi, 730kbps for cellular connections; but to also make available a version which is no more than 192kbps.
Both ART19 and Acast are supplying video encoded in five sizes: 1080p, 720p, 480p, 360p and 240p. ART19’s show is encoded to 30 frames per second. Acast’s uses 23.976fps. Both are US standards; Europe uses 25 or 50fps; Apple supports all of these.
I-frame playlists must be supplied (they are the things that add thumbnails as you scrub through a video). Both ART19 and Acast are supplying these.
Subtitles “may” be provided. The standard only uses WebVTT files. This is one of the standards in the transcript tag that Apple Podcasts already supports. Only ART19 is currently supplying subtitles.
The Apple specifications do offer “stereo video” and “immersive video", which is playable on an Apple Vision Pro unit. You should be able to produce 3D-like video, therefore, in your standard Apple Podcasts HLS stream, for those with Apple Vision. (Apparently around 400,000 people, incidentally)
The audio
The audio is a separate track, known as a “rendition”. That enables playback to continue uninterrupted when a user hits the “Turn Video Off” button; so your phone just continues to download the audio track and doesn’t bother downloading any video track any more. It also enables audio playback to be rock solid, even if the video isn’t. We’ve seen that first-hand: particularly when seeking through video, the audio starts almost immediately, but the video can take a few seconds to appear. This is good.
The presence of only one audio track suggests that there won’t be any opportunity to offer a different audio mix to the one in the video. We also understand that the audio track from the HLS is the only audio that will be heard by users of Apple Podcasts. If you’re on a device that copes with HLS (like an iPhone running iOS 26.4), your phone will never download the MP3; just the audio rendition within the HLS. So enabling video for an episode means the MP3 won’t get played. (The MP3 is still needed for things that don’t do HLS yet, like the HomePod, earlier iOS devices, or, er, the Apple TV).
We’ve said “one” track above; actually, the spec allows you to have multiple bitrates for the audio track as well. Apple suggests anywhere from 32 up to 160 kbps for the audio component; but the requirement for something that works for cellular at a total of 192kbps suggests that there might need to be a lower-quality audio track to pair with a low-quality video one.
The ads
Neither of the test shows visible in the Apple Podcasts app appear to have any advertising in it. But, we understand that ads will use HLS interstitials, which may form the basis of Apple’s billing. Interstitials (“ads") can be set to be not skippable, so if this is set, you can’t skip the ad once it starts playing - and not jumpable, so you can’t jump past an ad altogether on the scrub bar. We don’t have confirmation whether the Apple Podcasts app will honour either of these settings, but the Apple documentation seems to suggest that it will.
Things may change
This is all still in beta. Things may change between now and iOS 26.4 being released in, probably the end of March. There’s plenty that we don’t yet know; and we hope Apple Podcasts will be open with their documentation once they’re able to.
Theoretically, though, this does mean that the same HLS feed should work if you were to put it into an alternateEnclosure for other podcast apps, and should also work just fine on Android or other devices. There’s nothing proprietary here - just a carefully constructed HLS master playlist. And that’s good news for all of us.
