Definition
CTOR (click-to-open rate) and CTR (click-through rate) answer different questions. CTR tells you what percentage of all delivered emails resulted in a click. CTOR tells you what percentage of opened emails resulted in a click. CTOR isolates content performance from subject line performance.
When to Use Each
- CTR: Best for evaluating overall campaign effectiveness — it reflects both subject line quality (driving opens) and content quality (driving clicks)
- CTOR: Best for evaluating content effectiveness alone — it controls for open rate differences, making it ideal for A/B testing content variations
Example
Campaign A: 20% open rate, 5% CTR, 25% CTOR. Campaign B: 10% open rate, 4% CTR, 40% CTOR. Campaign B has worse overall performance (CTR) but better content (CTOR). The subject line needs improvement, but the content is strong.
Which Matters More
For most senders, CTR is the more practical daily metric. CTOR is most valuable when analysing content performance in isolation — such as comparing different email designs or copy approaches.
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
AIDA Model for Email
The AIDA model (Attention, Interest, Desire, Action) is a classic copywriting framework used to structure email campaigns that guide subscribers from awareness to conversion.
AMP for Email
AMP for Email is a Google-developed framework that allows email messages to include interactive elements like forms, carousels, accordions, and live content. It turns static emails into dynamic, interactive experiences directly inside the inbox.
Anchoring Effect in Email Marketing
The anchoring effect is a cognitive bias where the first piece of information presented (the anchor) influences subsequent decisions, used in email to frame pricing and value perception.
Announcement Email
An announcement email is a dedicated campaign that communicates a specific update, milestone, or change to subscribers, from product launches and feature releases to company news and events.