What is Ad fatigue?

Ad fatigue occurs when a target audience has seen the same creative so often that engagement falls and cost per acquisition rises, even though targeting and bidding have not changed. It shows up as a characteristic decay curve: frequency climbs, click-through rate falls first, then conversion rate, and CPA rises last.

Most paid social accounts see meaningful degradation once frequency passes roughly 2.5 to 3.5 impressions per user per week on a cold audience, and considerably sooner on small retargeting pools where the same people are reached daily. Ad fatigue is distinct from audience saturation, which is the related problem of having exhausted the addressable audience rather than worn out the creative — the tell is that saturation does not improve when you swap creative, and fatigue does. Diagnose it by segmenting performance by frequency band rather than reading the campaign average, which hides the decay. The remedy is a refresh cadence matched to spend: high-spend accounts typically rotate creative every two to three weeks, lower-spend accounts every four to six. The constraint is rarely knowing when to refresh; it is having enough new creative ready when the moment arrives.