Glossary
What is Unfilled impressions?
Also called: unfilled requests, unsold impressions
Unfilled impressions are ad requests that came back with no ad at all, so nothing was shown in the slot.
हिंदी में पढ़ेंIn Google Ad Manager reports, unfilled impressions are ad requests to the Ad Manager server, AdSense and Ad Exchange that did not return an ad. Despite the name, nobody saw anything: the slot stayed empty. AdSense reports show the same idea from the other side as coverage, the share of requests that returned an ad.
Ad Manager defines total ad requests as unfilled impressions plus the total code served count. So unfilled impressions are the missing part of your fill: the more of them you have, the lower your fill rate. They are inventory you offered and earned nothing from.
The usual causes are no demand for that visitor, country or ad size, floors set above every bid, and bids that arrived after the timeout. A house line item at priority 16 can catch requests that would otherwise go unfilled, though it earns nothing. Split unfilled impressions by country, device and size to see where to act.
Example
An ad unit gets 50,000 ad requests and 6,000 are unfilled. That means 12% of its requests (6,000 ÷ 50,000) returned no ad at all.
Why it matters to publishers
Unfilled impressions are unsold inventory. Tracking them by segment shows where demand, floors or timeouts need attention.