Key Points

  • The average publisher now works with too many partners, directly integrating with 24.5 sell-side technology platforms and authorizing 15.3 of these partners to initiate resold auctions.
  • Rebroadcasting supply chains account for over a third of all auctions, representing 37% of display auctions and 32% of video auctions.
  • Magnite leads SSP coverage at 95.7%, with PubMatic at 86.0% and Google at 76.4%, though these figures vary significantly by channel.
  • Durable supply chains (maximally direct paths to premium supply) represented 64% of all RTB bid requests and captured 69% of all DSP gross ad spend in February 2025.
  • Supply access is no longer a competitive advantage for SSPs, as every major publisher now partners with multiple exchanges.
  • The future will favor SSPs focused on demand generation rather than just supply access, as bidstream bloat forces DSPs to be more selective.

If you've been feeling like the programmatic advertising landscape gets more complex by the day, Jounce Media's March 2025 Supply Path Benchmarking Report confirms your suspicions. The latest data reveals some fascinating insights about where ad dollars are flowing, who's controlling them, and what this means for publishers looking to maximize their revenue potential.

Let's cut through the noise and focus on what actually matters to publishers.

Publishers Are Juggling Too Many SSP Partners

The average RTB-enabled publisher is now directly integrated with a staggering 24.5 sell-side technology platforms, according to Jounce's latest findings. What's more concerning? Publishers are authorizing 15.3 of these partners to initiate resold auctions.

This isn't just a matter of managing relationships - it's creating significant inefficiencies in the supply chain. Rebroadcasting supply chains (where your inventory gets resold without your control over the final ad decision) now account for 37% of display auctions and 32% of video auctions.

Translation: over a third of your ad impressions are taking the scenic route to advertisers, picking up fees along the way and potentially exposing you to fraud risk.

Who's Winning the Exchange Coverage Race?

If you're trying to figure out which SSPs deserve your attention, Jounce's data provides some clarity. As of late February 2025, the top exchanges by coverage are:

  1. Magnite: 95.7%
  2. PubMatic: 86.0%
  3. Google: 76.4%
  4. Index Exchange: 75.6%
  5. OpenX: 75.0%

Magnite currently dominates with supply integrations covering 95.7% of long-term DSP spend (it’s no wonder we chose to partner with them to bring our programmatic flex skins to market), while PubMatic covers 86.0%. Google Ad Manager's available supply supports 76.4% of long-term DSP spend.

However, these figures vary significantly by channel. For CTV specifically, Magnite leads with 99.0% coverage, followed by FreeWheel at 76.5% and PubMatic at 75.0%. In mobile apps, Google takes the lead with 77.7% coverage.


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Supply Access Is No Longer a Differentiator

Perhaps the most important strategic insight from the report is that comprehensive supply access has become table stakes rather than a competitive advantage. Jounce notes, "SSPs that achieve comprehensive supply access do not necessarily win the market."

In fact, the report reveals that every one of their 100 bellwether sellers (which collectively control 59% of DSP spend) partners with multiple SSPs. For example, Roku entered the RTB category in 2019 with an exclusive Magnite partnership and now has 9 widely deployed monetization partners.

This proliferation of SSP relationships creates what Jounce calls "bidstream bloat" - a growing problem for DSPs that must either process "many tens of millions of auctions per second" or squeeze most SSPs down to "negligibly small QPS allocations."

The Rise of Durable Supply Chains

Jounce defines durable supply chains as "RTB connections that will gain market share as media buyers implement supply path optimization strategies." These durable paths have two key characteristics:

  1. They're maximally direct (the seller controls the final ad serving decision)
  2. They lead to premium supply (not "cheap reach" or "made for advertising" inventory)

In February 2025, these durable supply chains represented 64% of all RTB bid requests and captured 69% of all DSP gross ad spend. Jounce expects these numbers to climb toward 100% in the coming years as buyers optimize their paths.

What's Coming Next

If Jounce's predictions hold true, we can expect:

  1. A flattening of supply access among leading SSPs
  2. SSPs focusing more on demand generation rather than supply access
  3. DSPs becoming more ruthless in de-duplicating the bidstream
  4. Publishers continuing to adopt multiple SSP partners to maximize revenue

What This Means for Publishers

For publishers, the message is clear: simply having your inventory available on exchanges isn't enough anymore. With every major open internet media company partnering with multiple SSPs, the winners and losers will be determined by their ability to generate demand.

While managing multiple SSP relationships gives you access to more demand, it also creates complexity. Smart publishers will focus on identifying which of their SSP partners are driving actual incremental revenue rather than just duplicating bids.

As an industry, we're moving toward a world where quality, directness, and transparency will triumph over complex, opaque supply chains. Publishers who embrace this shift now by focusing on durable supply chains will be better positioned for long-term success in the programmatic ecosystem.

The days of adding every possible SSP to maximize revenue are giving way to a more strategic approach - one where understanding your supply paths and optimizing for quality demand will ultimately drive better results than simply multiplying your monetization partners.

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