Walmart

Walmart's online store is the e-commerce arm of the largest retailer in the United States, combining its own inventory with a third-party marketplace.

Its advantage over pure online competitors is the store network: same-day pickup and local delivery run from physical locations, which shortens delivery times in ways a warehouse model cannot always match.

For sellers the marketplace has fewer participants than Amazon's, which means less competition per listing but also stricter approval requirements to join.