I noticed something strange today and I’m hoping someone can explain it.

On desktop, my sponsored product is sitting in position #4 on the first page for a core keyword. Great, right? But when I check the same keyword on the Amazon mobile app (same account, same Wi-Fi, same zip code), my ad is nowhere to be found until page 3 – and even then, it’s a different placement.

I understand that mobile has fewer slots per page. But the discrepancy feels too big. Is Amazon running two completely different ranking algorithms for desktop vs. mobile? Or is there something else going on (personalization, different auction pools, etc.)?

For those who have studied this, what are the key differences between PC and mobile ad ranking? And how should we adjust our bidding and targeting strategies to win on mobile, where most of our customers actually shop?

Any insights would be hugely appreciated.