Libsyn's website will let you indicate how many ad spots you want for each episode, and choose the precise placement for each spot.
To ensure the ads are appropriate for your podcast, Libsyn will let you block certain categories (such as alcohol or politics) to avoid having those inserted in your podcast. And you're very likely to get ads because Libsyn's fill rate averages 75%.
You can expect to earn around $10 per thousand downloads (CPM) for each ad after the revenue split with Libsyn.
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