A simple framework for testing email subject lines
Stop guessing. Test one variable at a time across five subject-line styles and let the data pick your default.
Subject lines decide whether the rest of your email matters. Yet most teams pick one by gut feel.
Five styles to rotate
- Curiosity — "The one change we made to onboarding"
- Benefit — "Cut reporting time in half this month"
- Urgency — "Last day: early pricing ends tonight"
- Personalization — "{{first_name}}, your Q3 plan is ready"
- Question — "Is your funnel leaking here?"
Run it properly
Split at least 1,000 recipients per variant, test one element at a time and judge on clicks, not only opens — privacy features inflate open rates.
Build a playbook
After six tests you'll see which styles your audience rewards. Make that your default and keep testing the runner-up.