Click-Through Rate (CTR) is the ratio of users who click on a specific link (like an ad, email, or button) to the total number of users who view the page or advertisement. It is the industry-standard metric for measuring 'Engagement' and 'Relevance.' CTR is calculated by dividing total clicks by total impressions. In paid search, a high CTR is rewarded by ad platforms with a higher 'Quality Score,' which lowers the cost-per-click and improves ad placement. A low CTR usually indicates that the messaging is not resonating with the audience, that the targeting is off, or that the call-to-action (CTA) is not compelling enough. Beyond advertising, CTR is vital for email marketing and SEO, helping teams understand how well their subject lines and meta titles are grabbing attention in a crowded inbox or search result page. Consistent monitoring of CTR allows growth teams to iterate on copy and creative to maximize the volume of traffic entering the top of the funnel.