Why CPMs cratered 22% in Q1 2026
Spend did not drop. Inventory exploded. The math behind the squeeze.
Quarterly CPMs fell hard in the first quarter, and the reason is not the one most publishers assume. It was not a collapse in demand.
It was not a demand problem
Total ad spend held roughly flat year over year. If you only watched your CPM line you would have concluded the buyers left. They did not. What changed was the denominator.
Inventory exploded
Ad-supported inventory grew faster than spend, and it is not close. New ad-supported streaming tiers, more aggressive ad density on the open web, and a wave of AI-generated pages all poured supply into the same auctions.
When spend is flat and inventory doubles, the clearing price does exactly what you would expect it to do.
Who felt it worst
The pain was not evenly distributed:
- Commodity, undifferentiated inventory took the full hit.
- Sites with strong first-party data and real audience held up far better.
- Premium, brand-safe environments saw the smallest decline.
What to do about it
You cannot fix the supply glut. You can make your inventory less of a commodity. Tighten ad density where it is hurting viewability, invest in the audience signals buyers will actually pay a premium for, and stop comparing this year’s CPM to last year’s as if the denominator were stable. It is not.