Click-through rate
Clicks divided by impressions. On remnant display it mostly measures how clicky the inventory was, not whether a person arrived.
Click-through rate (CTR) is delivery clicks divided by impressions. It is the first number most dashboards show.
On open-exchange remnant it is a weak quality score. Leftover inventory produces clicks readily. The June 2026 learning flight was read on CTR and later thrown out. The August 2026 Supply Bench pull (partial coverage) showed the same shape with grain: 93.4 percent of 1,149 placements had zero clicks, while seven domains produced 41.3 percent of clicks from 4.7 percent of impressions. Reseller CTR was 0.423 percent versus 0.184 percent direct. SSP CTR on the same creative ran from OPENX at 0.111 percent to SMARTADSERVER at 3.074 percent.
We do not treat those CTRs as engagement. We did not have an IVT vendor attached, so we also do not treat them as certified fraud.
Use CTR only as a contamination clue (implausible rates on a handful of domains). Judge the buy on our first-party traffic grade: real visits to the landing page, bot traps, and engagement on that page. Click-to-page-view is one input. A vendor invalid traffic tag is a hint, not the verdict.
The field note is CTR is a trap.