Walmart Marketplace GMV grew 34% last year. Amazon 3P grew about 9%. Most Amazon sellers are treating Walmart as a syndication afterthought. That is the arbitrage.

ACoS on Amazon is up. Organic placement is harder. Fees keep climbing. And the second-largest U.S. marketplace is sitting there with thinner competition and a growing buyer base.

Read that gap again. Then read your channel mix.

The Numbers That Should Change Your Channel Strategy

Revenue per seller is the metric that tells you which way a marketplace is bending. When GMV growth outruns seller count growth, every existing listing gets a bigger slice. That is Walmart right now.

Walmart Marketplace GMV: +34% YoY. Seller count: +18% YoY. The spread is the opportunity. More revenue available per active seller in 2025 than in 2024.

Amazon 3P, same period. GMV up roughly 9%. Seller count growing faster than that. Revenue per seller compressing. Different game, same calendar.

The Category Saturation Gap

In most product categories, Walmart Marketplace has 60 to 70% fewer active listings than Amazon. In some subcategories the gap is wider.

What that means in practice. A brand spending $50,000 in sponsored on Amazon to crack top-5 organic in a category can land top-3 organic on Walmart with a clean listing and a high in-stock rate. Content and ops still beat budget. That window does not stay open forever.

What the Winners Are Doing

Four operating principles separate the brands actually building a Walmart book from the ones running a stale catalog feed.

One. Treat it as a first-class channel. Dedicated catalog manager. Walmart-specific content. Walmart-specific pricing logic. Not a syndicated copy of Seller Central.

Two. Respect the algorithm differences. Walmart weights in-stock rate, price competitiveness, and fulfillment reliability harder than Amazon does. Perfect in-stock with mediocre content beats premium content with stockouts. Every time.

Three. Enroll in WFS. Walmart Fulfillment Services is the trust signal the algorithm looks for. WFS sellers see materially better placement outcomes. The reason is the delivery promise, and Walmart will not extend that promise to merchants it does not control end-to-end.

Four. Price the parity equation. Walmart monitors price parity against Amazon and other channels. If your Walmart price is higher, placement suffers. The architecture that maintains parity without eroding margin is the actual work.

The Window Is Narrowing

The brands that will own Walmart Marketplace in 2027 are spending the operational capital in 2026. Reviews compound. Ranking compounds. Supplier relationships with Walmart compound. The cost of catching up later is not a line item you want to model.

Walmart becoming a major channel is not the question. Whether you take share before the door closes is.

Three Questions to Pressure-Test

Does your team have a Walmart-specific pricing rule, or does the Amazon price determine the Walmart price by default?

What percent of your Walmart catalog is on WFS, and what is blocking the rest?

If Walmart category saturation doubles in the next 18 months, where is your moat?