Buy Box (Featured Offer)

The Buy Box (officially "Featured Offer") is the boxed section on the right of the Product Detail Page that contains the Add-to-Cart button, the Buy Now button, the seller name, and the delivery promise. Whichever seller wins the Buy Box receives essentially all of the listing's orders — >95% of shoppers never click "Other Sellers".

Brand-registered private-label sellers usually win their own Buy Box by default (they are the sole offer). The Buy Box becomes contested when:

• Multiple sellers offer the same ASIN (resellers, distributors, brand vs. unauthorised)
• The brand uses both FBA and FBM SKUs on one ASIN
• An unauthorised seller appears with a lower price

Why Buy Box loss silently kills ad performance

This is the most expensive blind spot in PPC. If you lose the Buy Box:

1. Ads continue to show and spend (the algorithm doesn't stop the auction).
2. Clicks land on the PDP.
3. The Add-to-Cart button is bound to the competitor's offer.
4. Your ad-attributed orders go to zero. Your spend does not.

ACOS goes from 22% to infinity overnight. The cause is invisible unless Buy Box health is monitored separately.

Buy Box determinants

Amazon's algorithm weights, roughly:

A 2% price increase can cost the Buy Box to an FBM competitor at the same price who has worse metrics — fulfilment usually wins.

Monitoring

A working operation polls Buy Box ownership per ASIN every 15–60 minutes during normal hours and every 5 minutes during Q4. Tools like AMALYZE alert on Buy Box loss in near real time using Amazon Marketing Stream inventory signals plus offer listings.

Common mistakes

• Running ads on an ASIN without monitoring Buy Box. Spend continues, conversion goes to zero.
• Pricing aggressively without checking competitor fulfilment. FBA at the same price wins over FBM.
• Ignoring unauthorised sellers. Brand Registry's "Report a Violation" tool plus Transparency are the long-term fix.
• Stockouts. Inventory ≤0 = no Buy Box, no matter your price.