Thanks to the growth of AI and its impact on workflows, decisioning and optimization, the digital ad marketplace has experienced rapid technological advancement.
Now, publishers and SSPs are stepping up their tech game as buyers demand outcomes, performance insights and impression-level data. As we look toward 2026, we can see key sell-side trends emerging: Vertical video content is boosting on-site engagement, sell-side decisioning is putting more power in publishers’ hands, and publishers are providing programmatic transparency like never before.
Vertical Video Becomes the Open Web’s New Front Door
This year, vertical video won’t just enhance publisher experiences; it will define them. Short-form is becoming the dominant language of the internet. Some leading publishers are already rebuilding homepages and article templates around immersive, swipe-first video streams.
This evolution will fundamentally change how users enter and navigate the open web, with vertical clips acting as a dynamic “front door” that funnels audiences into news, evergreen content and commerce experiences. Early-adapter publishers are focused on creating and curating vertical video from multiple content verticals and using it as part of a multi-format strategy. Emerging tech solutions will lower the barrier to entry for publishers of all sizes.
At the same time, the rise of AI-generated misinformation and deepfakes will push advertisers toward brand-safe vertical environments controlled by trusted publishers, elevating vertical video from a format to a standalone premium channel. Expect CMOs to carve out dedicated budgets for this inventory as attention and engagement become the core KPIs for digital storytelling. The open web will finally compete with walled gardens on the same creative canvas, but with one crucial advantage: credibility.
Sell-Side Decisioning Becomes the New Battleground for Performance
The next leap in programmatic efficiency won’t come from curated packages; it will come from smarter sell-side decisioning. Sell-side decisioning is a result of AI and machine learning, which enables SSPs to more efficiently analyze their troves of nuanced first-party publisher data.
Even in the face of signal loss, SSPs can now train models on desired campaign outcomes, making proactive and effective decisioning possible. AI and machine learning solutions also enable partners to create audiences, make and optimize bidding decisions before sending requests to demand partners, create and troubleshoot deal performance and gather bidding insights. These newfound data capacities empower SSPs to optimize for performance and produce better outcomes for advertisers.
SSPs are evolving from simple access points into real-time decision engines that determine which impressions to surface, which demand paths to prioritize and which low-quality supply to filter out before the auction even begins. This shift creates a cleaner, higher-signal supply layer by default, giving buyers performance gains without the manual work of curation. As identity erodes, decisioning becomes a new form of addressability, powered by context, intent and quality scoring rather than user IDs. The outcomes it drives will be exceptionally valuable, with economic uncertainty setting off waste-related alarms for buyers. The platforms that pull ahead will be the ones that make the most intelligent choices upstream, long before a bid is ever placed.
Transparency Becomes a Measurable Advantage
Programmatic transparency has long been treated as hygiene, but in 2026, it will become a competitive moat. As marketers gain clearer visibility into how impressions are sourced, scored and priced, transparency will directly correlate with lower media waste and higher ROI. Buyers will increasingly abandon ambiguous supply paths in favor of partners who can show, not tell: no MFA sites, no hidden fees, no black-box optimization. Studies have shown that 99% of programmatic spend went to environments with low risk to buyers, and that MFA sites lost significant market share in 2025. The sell-side success stories in 2026 will come from publishers that can effectively communicate the high quality of their inventory.
The rise of AI only heightens the demand for transparency. Marketers will insist on explainable automation that surfaces why certain impressions won and how decisions were made. This dynamic creates a two-tiered market: Systems built on radical clarity rise, while opaque platforms lose relevance in budget cycles driven by accountability. Increasingly, transparency will evolve from a compliance requirement into a performance driver.
Innovation on the sell-side market will influence the evolution of the whole ad market. We’ll see advertisers increasingly recognizing the value of the open web and closer partnerships with publishers and SSPs. And with increased adoption of tech solutions, a growing share of publishers will have the power to capitalize on these trends. Understanding the opportunities in those trends means more revenue in the pockets of quality publishers of all sizes.