What are HLS Interstitials?

HLS (HTTP Live Streaming) Interstitials are a feature introduced in 2021 by Apple that provides a simple way to schedule advertisements (such as prerolls, midrolls) and other interstitial content in HLS streams. Interstitials are treated as separate assets that can be scheduled onto a program timeline. They do not need to be stitched in with discontinuity tags anymore but can be directly referenced via their multivariant playlist. This makes it easier to schedule ads because you only need to point to their multivariant playlist from your primary content​.

HLS Interstitials can be used to create seamless transitions in video content between advertisements, other interstitials, and HLS streams. They also provide options to optimize ad inventory, fine-tune interstitial presentation, specify navigation restrictions for ads, and schedule early return in live scenarios, among other things​​.

In terms of scheduling, ads can be placed along the content's timeline or at the beginning or end of playback.

Currently, only a few players support them, such as Apple AVplayer (Quicktime and Safari still have issues) and Airplay; thus, most ad insertions are still done using discontinuities.

You can test our own implementation with this PRE CUE (preroll) HLS interstitial:
https://ireplay.tv/carsandroads/brands.m3u8

Incompatible players will simply skip the ad

Article written by
Sylvain Corvaisier

Independent streaming and iOS engineer

Last modified: December 28th, 2024