# Prerequisites for using overlay ads with MediaTailor
<a name="overlay-ads-prerequisites"></a>

The following prerequisites apply when using overlay ads with MediaTailor:
+ The workflow must be live, not video on demand (VOD).
+ The Ad Decision Server (ADS) response must be configured to return only non-linear ads in the VAST response. MediaTailor ignores any linear ads for the purposes of ad stitching.
+ The manifest must use a SCTE-35 time signal message with segmentation type `id=0x38` to invoke the overlay-ad feature.
+ The streaming provider must have control of the client-device application and be integrated with the MediaTailor client-side tracking API.