Reference / Glossary / Measurement
Fill Rate
The share of ad requests a publisher or app sends that return a paid ad. Unfilled impressions show house ads or nothing. Fill rate is a sell-side metric; buyers see its mirror image in available inventory and price.
Related terms
Cite this entry:
Agency Echelon. "Fill Rate." Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/glossary/fill-rate/