Ad fatigue happens when your target audience is seeing the same creative too many times. As a result, your audience is less likely to engage with your ad, resulting in dwindling marketing performance results. Ad fatigue drives KPI trends down and is a factor of concern for performance marketing managers. You can find out if your creative suffers are burning out based on the trends of your performance metrics (such as CPI or IPM), on a day-over-day, week-over-week or month-over-month basis. If the evolution of your KPIs for a specific creative or campaigns are trending downward, while you didn't make any major change in your campaigns' settings, you're likely to suffer from ad fatigue. The remedy is to update and refresh your creatives.