Open rate is the share of delivered emails that recipients opened, calculated as unique opens divided by delivered messages.
Category
Metrics
Also known as
email open rate
It has become a softer metric since Apple Mail Privacy Protection (introduced 2021) began pre-loading images and inflating opens, so it no longer cleanly measures real attention. It still helps for relative comparison and as a deliverability signal, but less as an absolute measure of attention.
In practice
Read open rate as a trend and a deliverability hint, not a precise engagement number, and pair it with clicks and downstream conversions. A campaign judged on opens alone can reward subject lines over outcomes.
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