How do A/B tests work in Content Builder? What variables can be tested and how is the winner determined?

A/B testing in Content Builder allows splitting your send audience to test up to 10 variants before sending the winner to the remainder.
Test variables:
— Subject line (most commonly tested)
— From name
— Email content (different content block variants)
— Send time (with or without Einstein STO)
Test setup: Define the test percentage (e.g., 10% to each variant) and the winner determination period (e.g., 4 hours after send).
Winner criteria:
— Open rate (unique opens)
— Click rate (unique clicks)
— Revenue (if MC is integrated with Commerce Cloud or e-commerce tracking)
Automatic winner send: After the winner determination period, Marketing Cloud automatically sends the winning variant to the remaining audience. Results include statistical confidence metrics to validate significance.