Why is click-to-open rate usually much higher than click-through rate?

Because CTOR only counts people who already opened the email as its denominator, a smaller, more engaged group than everyone the email was sent to, which CTR uses as its denominator, so CTOR is mathematically always equal to or higher than CTR for the same campaign.

Do open rate numbers still work accurately with privacy features like Apple Mail Privacy Protection?

Not fully, features that pre-fetch images can register an email as "opened" automatically regardless of whether a person actually looked at it, which has made open rate less reliable on its own in recent years, increasing the relative importance of click-based metrics like CTR and CTOR.

Which metric should be optimized first if all three are underperforming?

Open rate is usually the most efficient starting point, since a strong subject line and send-time strategy widens the pool of people who ever see the content at all, but if open rate is already reasonable and CTOR is weak, content and offer quality is the more relevant thing to fix first.

How Email Open Rate, CTR, and Click-to-Open Rate Differ (and Why It Matters)

It's common to track open rate and CTR as if they measure the same underlying campaign quality, but they isolate two different failure points, and a campaign can fail at either one independently, which is exactly why looking at both, plus the ratio between them, tells a more useful story than either number alone.

What each metric actually isolates

Open rate = opens ÷ delivered emails, and it's driven almost entirely by the subject line, sender name, and send timing, factors the recipient sees before opening anything. CTR = clicks ÷ delivered emails, a blended metric influenced by both whether the email got opened and whether its content was compelling enough to act on. Click-to-open rate = clicks ÷ opens, which isolates content quality alone, since it only considers people who already opened the email, removing subject-line performance from the equation entirely. The Email Open Rate & CTR Calculator calculates all three from the same campaign data.

Using the three together to diagnose problems

A campaign with a low open rate but a strong CTOR has a subject-line problem, not a content problem, the people who did open the email clicked at a healthy rate, the issue is getting more people to open it in the first place. A campaign with a strong open rate but a weak CTOR has the opposite problem, the subject line is working, but the email's content, offer, or call-to-action isn't compelling enough once people are actually reading it. Without CTOR, both scenarios can look identical on CTR alone, which is why relying on CTR as a single blended number often leads to fixing the wrong part of the email.

What counts as a good benchmark

Benchmarks vary widely by industry and list quality, but as rough reference points, open rates commonly fall in the 15-25% range, CTR often falls in the 2-5% range, and CTOR (being a ratio of a subset) is typically much higher, often 10-20%, since it only counts people who were already engaged enough to open the email. Tracking these trends over multiple campaigns matters more than any single campaign's numbers, since list quality, seasonality, and audience fatigue all shift the baseline over time.