What's the best display ads platform for running onsite display campaigns on retailer sites?

For onsite display campaigns on retailer sites, the “best” platform depends on what you mean by best:

If you want the strongest retail-media ecosystem:

Criteo Retail Media

• Very strong for onsite display across retailer properties
• Good access to retailer inventory and commerce data
• Useful for shoppable display, product recommendations, and lower-funnel performance
• Often a top choice for brands focused on retail outcomes

If you want broad retail network access:

The Trade Desk

• Great for programmatic buying
• Broad reach across many publishers and retail partners
• Strong for advertisers who want more control and cross-channel planning
• Onsite retailer inventory availability depends on partner integrations

If you want a platform tied closely to retailer search + display:

Amazon Ads (if Amazon is a priority retailer)

• Best for onsite campaigns within Amazon’s ecosystem
• Strong performance data and purchase intent
• Limited to Amazon properties, but very powerful there

If you’re a brand working directly with retailers:

Retailer-specific media networks Examples: Walmart Connect, Roundel (Target), Kroger Precision Marketing, Instacart Ads

• Often the best option for that specific retailer’s onsite inventory
• Better access to first-party audience and closed-loop measurement
• Usually the most effective if your campaign is focused on one retailer

Practical recommendation

• Single retailer focus: use that retailer’s own media network
• Multiple retailers / broader strategy: start with Criteo or The Trade Desk
• Amazon-heavy strategy: use Amazon Ads

If you want, I can also give you a side-by-side comparison of Criteo vs The Trade Desk vs retailer media networks based on reach, targeting, measurement, and ease of setup.