Marketing Calendar 2026
Click-to-open (CTO)
Click-to-open rate (CTO) is a valuable but sometimes misunderstood email metric. It shows how many people who opened your email clicked on something inside it. Usually a link, call to action, or image. In short, it measures how engaging your email content was once someone took that first step and opened it.
CTO is often confused with CTR (click-through rate), which looks similar but tells a slightly different story. Click-through rate is the number of people who clicked your email link divided by the number of emails you sent. However, the CTO focuses on the people who opened it, not everyone you sent it to. That makes it more about content performance: was your email clear, convincing, and relevant, rather than delivery or subject line success?
Marketers lean on the CTO to understand whether their email copy and design are doing the job. If your open rate is high but CTO is low, your headline worked but the email body didn’t follow through. The message may have been too long. Or confusing. Or the call to action wasn’t clear. Conversely, if your open rate is low but your CTO is strong, it might be time to work on subject lines and sender details.