Click-through rate, or CTR, measures the percentage of delivered emails where a recipient clicked at least one link. It is calculated by dividing unique clicks by delivered messages, and unlike open rate it reflects a deliberate action, making it one of the most trustworthy indicators of genuine engagement with your content.
Because a click requires intent, CTR is far more resistant to the privacy inflation that undermines open rate. When someone clicks a link, they have actively chosen to act on your message, which is why marketers increasingly treat CTR as the primary measure of whether an email's content and call to action resonated.
A related and often more insightful metric is click-to-open rate (CTOR), which divides clicks by opens rather than by all delivered messages. CTOR isolates how effective the email's body and offer were among people who actually opened it, separating content performance from subject-line performance.
Clicks are tracked by rewriting links so they pass through the sending platform's redirect before reaching the destination. This enables measurement but means overuse of tracked, shortened, or mismatched links can itself trigger spam filters, so a clean linking strategy supports both accurate CTR and good deliverability.