Microsoft Invest Shuts Down February 28: A Demand Path Checklist for Sellers

Microsoft Invest, the demand-side platform that grew out of AppNexus and Xandr, shuts down on February 28. Microsoft first told clients in May 2025 that it would close the DSP and focus on Microsoft Curate for curated deals and Microsoft Monetize for publishers. In October, it named Amazon DSP as its preferred partner for advertisers moving off Invest, and Microsoft Monetize joined Amazon's Certified Supply Exchange program.

For publishers, a DSP closing is easy to ignore because you never contracted with it directly. That is a mistake. Buyers who used Invest are moving their campaigns, deals and targeting somewhere else in the next three weeks, and anything tied to the old platform on your side will quietly stop spending on March 1.

What is changing, and what is not

• Closing: the Invest DSP, used by agencies and advertisers to buy programmatically.
• Continuing: Microsoft Monetize, the sell-side platform many publishers use, and Microsoft Curate, which packages supply into curated deals.
• Moving: buyer budgets, audience data and campaign setups, to Amazon DSP or whichever other DSPs those buyers choose.

So this is not a supply-side outage. If you sell through Monetize, your SSP relationship continues. What changes is which buying platforms show up in your auctions and how your deals are wired.

A seller checklist for the next three weeks

1. Find every deal that targets Invest buyers

Private marketplace and programmatic guaranteed deals are set up for specific DSP seats. Pull a list of all active deals, on every SSP you use, where the buyer seat belongs to Invest. For each one, contact the buyer or agency and ask where the campaign is moving. The deal will need to be recreated or re-targeted to the new DSP seat. Deals that are not migrated will simply stop spending.

2. Don't let the new deals lose their terms

When deals are rebuilt on a new platform, details get lost: floor prices, targeting, frequency settings, creative requirements, brand safety rules. Compare the new setup line by line against the old one. This is exactly the kind of manual re-entry that causes deal troubleshooting headaches in April.

3. Watch for gaps in March revenue

Even well-managed migrations leave gaps. Some buyers will pause while they rebuild audiences and learn a new platform. Set up reporting that isolates revenue from buyers who used Invest, so a March dip can be traced to its cause rather than blamed on seasonality or your own settings.

4. Check how your inventory reaches Amazon DSP

If a meaningful share of former Invest spend lands in Amazon DSP, the question becomes which supply paths Amazon DSP uses to reach your inventory. Look at which of your SSPs are integrated with Amazon DSP and how your inventory appears there. If you have a direct relationship with Amazon Publisher Services, confirm that relationship is set up to benefit from that demand.

5. Keep ads.txt and sellers.json accurate

A DSP closing does not require ads.txt changes on its own, because ads.txt lists the sellers of your inventory, not the buyers. But demand shifts are a good moment for a hygiene pass. Make sure every SSP and reseller that should be selling your inventory is listed correctly, with the right seller account ID and relationship type, and remove entries for partners you no longer work with. Buyers moving to a new DSP will re-evaluate supply paths, and a messy ads.txt file gives them reasons to cut you out.

Why B2B publishers should pay extra attention

Many B2B and trade publishers run a larger share of revenue through a small number of deals with specialist agencies and technology advertisers than consumer sites do. Losing one or two well-paying deals in a migration can show up as a noticeable revenue hole. If that describes your business, call your top buyers this week rather than waiting for them to contact you. Ask specifically:

• Which DSP they are moving to and when the first campaigns will run
• Whether they need new deal IDs from you, or will buy through a curated package
• Whether their audience segments, including any first-party or account-based data, will carry over
• Who on their side owns the migration

The broader signal

Microsoft said at the time that the traditional DSP model did not align with its goals in an increasingly conversational, AI-driven advertising landscape. Whatever the reasons, the practical effect is that one fewer independent buying platform bids into open-web auctions. Consolidation on the buy side tends to mean fewer, larger buyers with more leverage over supply paths.

The best defense for sellers is to be easy to buy and easy to trust: clean supply chain data, direct paths where they make sense, well-documented deals, and responsive support when a buyer needs something changed quickly. Those qualities matter every day, but they matter most during migrations like this one, when buyers are rebuilding their plans and deciding which sellers make the new list.

Quick summary

1. Inventory all active deals with Invest buyer seats.
2. Contact buyers and confirm their new DSP and timing.
3. Recreate deals carefully, preserving terms.
4. Set up reporting to track former Invest spend through March.
5. Review Amazon DSP access paths.
6. Clean up ads.txt and sellers.json while you are at it.

Nineteen days is enough time to do this properly if you start now. Assign one person to own the list, track each deal to confirmed migration or confirmed end, and review the results in the first week of March, when any deal that was missed will show up as zero delivery rather than a gradual decline.