Which metric is crucial for assessing direct engagement with an online ad?

The click-through rate (CTR) is a vital metric for assessing direct engagement with an online ad. This metric reflects the percentage of users who click on an advertisement after seeing it, providing insight into how compelling and relevant the ad is to its audience. A higher CTR indicates that the ad successfully captures attention and encourages interaction, which is essential for measuring effectiveness in digital advertising campaigns.

In contrast, cost per impression measures how much it costs advertisers each time their ad is displayed, without considering user engagement. Conversion rate focuses on the percentage of users who take a desired action after clicking the ad, such as making a purchase, which is more related to post-engagement success rather than initial interaction. Return on ad spend calculates the revenue generated for each dollar spent on advertising, reflecting overall campaign profitability rather than the immediate response from users to the ad itself. These metrics are important but do not specifically gauge how effectively an ad engages viewers at the first point of interaction, which is the essence of the click-through rate.