What Is Click-to-Open Rate in Email?

Click-to-open rate, or CTOR, is a ratio of email clicks to reported opens, usually using unique clicks and unique opens. It depends on how the provider identifies and filters both events. Because privacy features can affect reported opens, CTOR does not tell you exactly what share of people who read an ad clicked it.

Published and updated 5 November 2026.

Dupple publishes Techpresso, AIpresso, Devshot, Cyberpresso, Finpresso and MarketingShot, and sells sponsorships in them. Dupple publishes this guide and sells newsletter placements.

The formula and a worked example

A common definition divides unique clicks by unique reported opens and multiplies the result by 100. Campaign Monitor's CTOR glossary, checked on 5 November 2026, describes that unique-click and unique-open formula. Ask each provider whether its numerator and denominator use the same issue, population, time window and filtering rules.

Table: a hypothetical issue using the same unique-event basis for the two measures.

The example is arithmetic, not a benchmark or a campaign result. If a report counts every click rather than unique clickers, the numerator can include repeated actions. If it uses unique opens but total clicks, the resulting number is a different ratio. Ask what happens when a person clicks without an open being recorded and how automated activity is filtered.

What Dupple's historical snapshot shows

Our data, verified November 2026: In a Dupple engagement snapshot read from the email platform on 11 October 2026, MarketingShot had 35,570 active subscriptions, a 31.8% reported open rate and a 1.8% reported click rate. Dividing the reported click rate by the open rate gives a 5.7% click-to-open figure after rounding. The six-newsletter benchmark study records the source; across the six lists it covers 925,191 active subscriptions, not deduplicated people.

The platform reports trailing averages but the source does not state the exact trailing window or the number of issues in that average. This is newsletter-wide activity, not clicks on a particular sponsor placement. Rates are rounded and the ratio is derived from those reported rates; confirm the underlying event definitions before interpreting it as a ratio of unique individuals. Dupple's platform figures are not independently audited.

The observation cannot tell you how many MarketingShot readers saw an ad or predict a future campaign. List mix, content, delivery and measurement can differ across issues. One list's historical result should not be presented as a universal target or as proof that a larger or smaller newsletter causes a particular response.

Why the open denominator needs care

An open is typically inferred from the retrieval of remote email content, subject to the platform's method. Apple's Mail privacy guidance, checked on 5 November 2026, describes background downloading of remote content under privacy settings. Such downloads can contribute to reported opens without establishing that a person looked at the message.

CTOR divides by the reported-open number, so an increase in that denominator can lower the ratio even if the measured clicks do not change. Conversely, an unrecorded open can change the relationship between the two events. A click is evidence of an interaction under the provider's rules, but automated security systems and repeated activity can also affect click reporting. Ask how the provider filters those events.

Campaign Monitor's glossary describes a unique-click to unique-open calculation. Its interpretation of an open as an actual view should be read alongside Apple's privacy explanation: the reported event does not by itself prove a human viewed the email or the sponsor. Providers can use different definitions, so confirm the exact calculation on the report you receive.

CTOR, click rate and sponsor clicks

CTOR and click rate answer different questions because their denominators differ. A click rate may divide clicks by delivered messages or another stated base. CTOR divides by reported opens. Neither ratio automatically isolates a sponsor's link: a newsletter can contain editorial links and several calls to action.

If evaluating a sponsorship, request clicks attributed to the specific sponsor destination as well as newsletter-wide measures. Ask whether the number represents unique clickers or total clicks, how redirects and automated checks are handled, and what period the report covers. The Primary Ad guide describes one in-issue format; a dedicated send has a different context and should be evaluated on its own terms.

A publisher's newsletter-wide CTOR can help describe its reporting, but it does not establish what a sponsor received in one issue. A sponsor click is an interaction, not automatically a qualified inquiry or a sale. Agree on the desired action, the landing page and qualification rules before the issue runs.

How to compare two reports

First, check that the numerator has the same meaning. One report may count distinct clickers on the advertiser's link; another may count all clicks across the issue. Second, check the denominator. Unique reported opens, total opens and delivered messages are different bases. Third, compare the periods, including how long after delivery each report continues to collect events.

Ask about privacy features, bot filtering and list inclusion. A provider may suppress known automated activity differently from another platform. A report covering all content in an issue also answers a different question from a report covering only a sponsor link. If a definition is missing, keep that part of the comparison uncertain instead of presenting a precise ranking.

Retain the creative, placement and offer alongside the numbers. A different call to action, issue topic or landing page can change observed activity. The newsletter buying guide provides questions to request before booking, and the sponsorship ROI guide explains how to connect activity to a business objective.

A practical measurement plan

Define the action that matters before publication: a documentation visit, event registration and qualified inquiry are different outcomes. Use consistent tags on the advertiser's destination and test them on mobile and desktop. Decide who will verify the link, review the report and follow up on any form submission. State what makes an inquiry relevant to the campaign.

Dupple says its campaign reports include opens, clicks, click-through rate, benchmarks and corporate domains that engaged. Ask for an example report and the definitions applicable to the proposed format. Compare the provider's data with your own analytics while allowing for consent, redirects and filtering. A difference between systems is a reason to inspect the methods, not proof that either number is a count of human ad views.

After a defined follow-up period, review both activity and qualified outcomes. Preserve the issue date, approved copy, audience definition and landing page with the result. A single placement is a limited observation; if several elements change in a later test, its difference cannot be attributed to one factor alone. The CPM guide and advertising data page provide additional measurement context.

Before comparing proposals, note the actual placement as well as the rate. Dupple's Primary Ad page and dedicated-send page describe two formats with different contexts. Ask the publisher which links are included in a report and whether a separate send is measured using the same rules as an in-issue sponsorship. Keep an unanswered definition visible when sharing results with colleagues.

What we could not verify

The historical Dupple source does not state the exact trailing period or issue count behind the platform averages. Dupple's platform figures are not independently audited, and the snapshot does not isolate a sponsor's results. Other providers' figures are self-reported unless an audit is identified. Open and click definitions and filtering can differ across platforms; privacy-related downloads prevent an open from proving a human ad view. We cannot predict a campaign outcome.

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