Just came across this article from December of 2025. Thought it would be interesting to share.

12/3/2025

Quick Summary:

Delivery speed now weighted 25-30% in Buy Box algorithm (up from 15%)

Same-day/next-day delivery sellers seeing 18% higher Buy Box win rate

Price competitiveness threshold widened to 2-3% vs previous 1%

FBM sellers without Premium Shipping losing Buy Box to FBA at higher prices

What's Happening

Amazon has quietly shifted the Buy Box algorithm to prioritize delivery speed over price. Sellers report losing 15-20% Buy Box share despite maintaining competitive pricing. Same-day and next-day delivery sellers are now seeing an 18% higher Buy Box win rate compared to standard shipping offers.

This represents a fundamental shift in how the Featured Offer is determined. For years, price was the dominant factor. Now, delivery speed appears weighted at 25-30% of the algorithm, up from an estimated 15% previously.

New Buy Box Algorithm Weighting

Delivery Speed

25-30%

Up from ~15% previously

Buy Box Win Rate

+18%

For same-day/next-day sellers

Price Tolerance

2-3%

Widened from ~1%

Price No Longer King

The price competitiveness threshold has widened to 2-3% vs the previous 1%. This means a seller offering next-day delivery at $20.50 can win the Buy Box over a 2-day delivery seller at $20.00.

Updated Buy Box Factors

Factor Previous Weight Current Weight Impact

Delivery Speed ~15% 25-30% ↑ Major increase

Price ~35% ~25% ↓ Reduced

Fulfillment Method ~20% ~20% → Stable

Seller Metrics ~20% ~15% ↓ Slight decrease

Stock Availability ~10% ~10% → Stable

Note: These weights are estimated based on seller reports and third-party analysis. Amazon does not publicly disclose exact Buy Box algorithm weighting.

Impact on Sellers

FBA Sellers Gain Advantage

FBA sellers with inventory in Prime-eligible fulfillment centers benefit most. Amazon's network enables same-day and next-day delivery, giving FBA an inherent Buy Box advantage over FBM sellers without Premium Shipping.

FBM Sellers Face Pressure

FBM sellers without Premium Shipping are losing Buy Box to FBA competitors even when priced 2-3% lower. Standard 3-5 day shipping is no longer competitive for high-velocity products.

Key Implications

Hybrid strategy recommended: Split inventory between FBA (for Buy Box) and FBM (for backup stock and special handling).

Seller Fulfilled Prime matters more: FBM sellers meeting SFP requirements can compete, but the 99% on-time delivery threshold is strict.

Regional warehousing becomes critical: Inventory positioned near major metros enables faster delivery and higher Buy Box share.

What You Should Do Now

1.

Audit Your Buy Box Share: Check Business Reports in Seller Central. If Buy Box percentage dropped despite stable pricing, delivery speed is likely the cause.

2.

Review Your Fulfillment Mix: For top-selling ASINs, consider shifting more inventory to FBA. Use Nova's P&L Dashboard to calculate the margin impact.

3.

Enable Premium Shipping (FBM): If you fulfill orders yourself, enroll in Premium Shipping programs that offer same-day or next-day options.

4.

Explore Seller Fulfilled Prime: Meet the 99% on-time delivery requirement, offer same-day/next-day shipping, and fulfill on weekends to qualify.