Podcast ads bought via Ad Manager Auction are delivered through Streaming Ad Insertion (SAI), Spotify’s own ad technology. With SAI, Spotify can record an ad impression in real time, as soon as the ad starts playing, rather than when it is downloaded. This allows advertisers to understand confirmed ad impressions and unlocks first-party insights into audience, reach, frequency, and clicks.

In order for your ad to serve in podcasts,  you must be eligible for In-Stream placement.