Tap through rate, also known as TTR, is a metric used to measure the effectiveness of a digital advertisement or link. It represents the percentage of users who tap on an ad or link after seeing it, compared to the total number of impressions. A high tap through rate indicates that the ad or link is engaging and relevant to the target audience, while a low TTR may suggest that the ad is not resonating with users. TTR is an important measure for advertisers and marketers to track, as it can help them optimize their campaigns and improve their return on investment.