Click-through rate (CTR) is the ratio of users who click on a specific link to the number of total users who view a page, email, or advertisement. It is commonly used to measure the success of an online advertising campaign for a particular website as well as the effectiveness of email campaigns

The purpose of click-through rates is to measure the ratio of clicks to impressions of an online ad or email marketing campaign. Generally the higher the CTR the more effective the marketing campaign has been at bringing people to a website. Most commercial websites are designed to elicit some sort of action, whether it be to buy a book, read a news article, watch a music video, or search for a flight. People rarely visit websites with the intention of viewing advertisements, in the same way that few people watch television to view the commercials.

While marketers want to know the reaction of the web visitor, with current technology it is nearly impossible to quantify the emotional reaction to the site and the effect of that site on the firm’s brand. However, click-through rate is an easy piece of data to acquire. The click-through rate measures the proportion of visitors who initiated an advertisement that redirected them to another page where they might purchase an item or learn more about a product or service. Forms of interaction with advertisements other than clicking is possible, but rare; “click-through rate” is the most commonly used term to describe the efficacy of an advert

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