Show the same people the same creative long enough and response cools. Frequency climbing while CTR falls — that scissor shape — is the fatigue signal.
Separating it from other causes
A falling CTR makes you want to swap creative immediately. Check frequency first.
Frequency ↑ with CTR ↓ → fatigue is likely. Rotate creative or widen the audience.
Frequency flat with CTR ↓ → probably not fatigue. Look at competition, season, targeting changes. New creative will not fix this one.
A drop in blended CTR is also frequently just a larger mix of new assets still in learning.
When rotating
Swapping every underperformer at once destabilises learning. Replace the bottom few instead.
No. Fatigue requires [frequency](/glossary/frequency) to be rising alongside it. If frequency held flat while CTR fell, the cause is likely outside the creative — competition, seasonality, or a targeting change.
If frequency and CTR move together, is fatigue confirmed?
That is association, not proof. Confirming it means changing only the creative and checking whether response recovers.