Microsoft Prebid Server Premium: status after Xandr, how PSP works and alternatives

Microsoft describes PSP as a "self-service, server-side solution" that runs on open-source Prebid Server Go. It says PSP gives "access to over 200 demand partners" (company claim), across web, mobile web, app, OTT and AMP, in display, native and video (Microsoft Learn, 21 October 2025).

The published list is longer than the headline. On 2 November 2026 Microsoft's demand-partner table had 341 rows, 332 of them marked as enabled. Microsoft says new open-source adapters are "generally added to PSP within two weeks" (Microsoft Learn, 2 November 2026). The list includes Index Exchange, Magnite, OpenX and PubMatic, and a separate section for Amazon's APS adapter in limited beta.

PSP serves two kinds of publisher. Some use Microsoft Monetize as their ad server. Others keep another ad server, such as Google Ad Manager, and send supply to Monetize as an exchange (Microsoft Learn). If you want managed Prebid Server hosting from Microsoft, PSP is the product name to use.

Yes, on the evidence available on 9 November 2026. Microsoft closed its buy-side platform, Microsoft Invest, but kept its publisher platform. On 14 May 2025 it said it would stop supporting media buying through Invest from 28 February 2026, and that it would keep enhancing Microsoft Monetize for publishers (Microsoft Advertising, 14 May 2025). The buyer's side of that change is covered in life after Microsoft Invest.

The product has not been renamed. Microsoft Learn still calls it Prebid Server Premium, and Prebid.org lists it under Microsoft Monetize (Prebid.org, accessed 9 November 2026). We found no retirement notice in the PSP pages or the Monetize release notes.

PSP sits behind Monetize rather than beside it. Inventory must reach Monetize first, and PSP then adds Prebid Server demand to the same auction.

1. Connect inventory to Monetize. Direct-supply publishers can use Prebid.js, the Prebid Mobile SDK, AMP, or existing /openrtb2 and video-tag integrations (Microsoft Learn). For Prebid Mobile, the public host is https://ib.adnxs.com/openrtb2/prebid, which the SDK shipped as a built-in setting until version 3.0 (Prebid Mobile 3.0 API changes).
2. Add demand partners and configurations. You set global settings, add each partner and map your inventory to its IDs. Each seller needs its own contract with each demand partner (Microsoft Learn).
3. Run one auction. Partner bids compete with Monetize marketplace bidders under one global timeout. Microsoft suggests starting near 250 milliseconds and with three or four partners, then adding more (Microsoft Learn).
4. Sync users. Partners are synced through the user-sync URLs in their open-source bidder files. A partner that cannot handle a redirect macro can use a fixed /prebid/setuid URL on ib.adnxs.com (Microsoft Learn, 15 December 2025).
5. Read the reports. The PSP Health Analytics report is built from sampled logs and kept for 99 days. Microsoft says not to use it for final delivery or spend; the Monetize historical report does that job (Microsoft Learn, 6 July 2026).

A sampled health report is common in managed hosting, but it changes how you debug. Request-level checks go through the PSP Request Response Sampler instead. General Prebid Server debugging is covered in Prebid Server analytics and debugging.

The Prebid lineage is real. Prebid.org says AppNexus, now part of Microsoft, created Prebid.js (Prebid.org). A Microsoft representative chairs the Prebid Server committee, and Microsoft holds a board seat (Prebid.org committees; Prebid.org board).

Microsoft publishes no price for PSP on Microsoft Learn, and Prebid.org's listing gives none either (Prebid.org listing). Because each seller signs its own contract with every PSP demand partner, part of the economics sits in those contracts (Microsoft Learn). Microsoft's own fee for running PSP is not disclosed.

Questions worth asking before you sign:

• Is PSP billed as a share of revenue from PSP-won impressions, a flat fee, or inside your Monetize terms?
• Who pays you for impressions that PSP partners win: Microsoft or each partner?
• Which Prebid Server Go release runs in production, and how fast were the June 2026 critical fixes applied (GitHub advisory)?
• What notice period applies if Microsoft changes or retires PSP?

Strengths

• Close to the source. Prebid.js began at AppNexus, now part of Microsoft, and a Microsoft representative chairs the Prebid Server committee (Prebid.org).
• Wide adapter coverage. The partner list tracks open-source adapters, with new ones usually added within two weeks (company claim) (Microsoft Learn).
• APIs for set-up. Configurations, partners and parameter mappings can be managed through APIs as well as the interface (Microsoft Learn).
• Long-form video. A dedicated service handles podded video requests (Microsoft Learn).

Limits

• Access is restricted. Microsoft says PSP is not available to all customers (Microsoft Learn).
• It needs Monetize. Inventory must be integrated with Monetize before PSP can sell it, so PSP is not a stand-alone host.
• Sampled health data. The main troubleshooting report estimates volumes from samples.
• Shared infrastructure changes. Setups that relied on Microsoft's public Prebid Cache had to move by 30 April 2026 (Microsoft Learn).

• Any PSP fee, revenue share or minimum, and how payment flows for impressions won by PSP partners.
• Named publishers using PSP.
• Which Prebid Server Go release runs in production, and when Microsoft applied the 8 June 2026 advisory fixes.
• Any plan to rename or retire PSP. We found none in Microsoft Learn, in the Monetize release notes (latest entry 1 April 2026) or in a web search on 9 November 2026.
• What the "Enabled in Prebid" column in the partner table means in practice for the 8 adapters marked "No" (Microsoft Learn).

1. Microsoft Learn, "Prebid Server Premium" (last updated 21 October 2025). https://learn.microsoft.com/en-us/xandr/monetize/prebid-server-premium
2. Microsoft Learn, "Prebid Server Premium demand partner integrations" (2 November 2026). https://learn.microsoft.com/en-us/xandr/monetize/prebid-server-premium-demand-partner-integrations
3. Microsoft Learn, "Prebid Server Premium Analytics" (6 July 2026). https://learn.microsoft.com/en-us/xandr/monetize/prebid-server-premium-analytics
4. Microsoft Learn, "Set Up Prebid Server Premium" (21 October 2025). https://learn.microsoft.com/en-us/xandr/monetize/set-up-prebid-server-premium
5. Microsoft Learn, "Integrate with PSP" (21 October 2025). https://learn.microsoft.com/en-us/xandr/monetize/integrate-with-psp
6. Microsoft Learn, "Non-prebid integrations with PSP" (21 October 2025). https://learn.microsoft.com/en-us/xandr/monetize/non-prebid-integrations-with-psp
7. Microsoft Learn, "PSP common issues and best practices" (21 October 2025). https://learn.microsoft.com/en-us/xandr/monetize/psp-common-issues-and-best-practices
8. Microsoft Learn, "Prebid Server Premium identity and user syncing" (15 December 2025). https://learn.microsoft.com/en-us/xandr/monetize/prebid-server-premium-identity-and-user-syncing
9. Microsoft Learn, "Prebid Server Premium Services (APIs)" (22 October 2025). https://learn.microsoft.com/en-us/xandr/digital-platform-api/prebid-server-premium-services
10. Microsoft Learn, "Prebid Server Premium Flexible Configurations" release note (9 January 2025). https://learn.microsoft.com/en-us/xandr/monetize/release-notes-20250109