How to A/B test subject lines and email content

How to in Kit

1. Open Kit And Navigate To Broadcasts: In Kit, go to the left navigation and click Broadcasts to view your list of broadcasts and drafting options.
2. Edit Or Create Broadcast: Open an existing Broadcast you want to test, or start a new one by clicking Create Broadcast.
3. Enable A/B Testing: In the Broadcast editor, locate the Run an A/B Test toggle in the right sidebar and switch it on. Alternatively, click the flask icon next to the subject line to enter A/B test settings.
4. Choose A/B Test Type: From the A/B test options, select Subject lines as the test type.
5. Enter Subject Line Variants: Use the default two fields to input Subject Line Variant A and Variant B. If you are on Creator Pro, click + Add another subject line to include up to five variants.
6. Fill Variant Details: Ensure each variant is clear and distinct. Label them clearly (e.g., Variant A, Variant B, etc.).
7. Access Settings Tab: Switch to the Settings tab within the A/B test panel to configure duration.
8. Set A/B Test Duration: Use the slider or type a value in the minutes field to set a duration between 30 and 240 minutes (240 minutes is the default).
9. Save A/B Test Settings: Click Save in the A/B test panel to apply and lock in your variant setup and duration.
10. Send or Schedule Broadcast: Return to the main Broadcast view and choose Send Now or Schedule to delivery. The A/B test will run automatically as configured.
11. Edit An Existing A/B Test: If needed, click the flask icon next to the subject line or click Edit A/B test in the right sidebar to modify variants or duration.
12. End A/B Test Early: If you want to stop the test early, open the Broadcast's Analytics report, click the three vertical dots, and select Cancel A/B test.
13. Handle Test Cancellation: If canceled, the Broadcast will only be sent to test recipients. To complete delivery, navigate to Recipients, select those who have already received the email, tag them (e.g., "Cancelled A/B test"), duplicate the Broadcast, and send to the remaining recipients excluding the tagged ones. Remove the temporary tag after completion.
14. Review Results: Open the Analytics page to view per-variant open rates. The winning variant is highlighted with a green trophy when the test ends.
15. Test Email Content (Optional): If you also want to test content, switch the A/B test type to Content and repeat steps 6–12 for content variants, ensuring adequate sample sizes.
16. Automatic Winner Rollout: After the test completes, Kit automatically sends the winning subject line (and content, if tested) to the remaining recipients.