Subject Line Tester and Checker

Paste a subject line. Get an AI score out of 100, plus concrete feedback and rewrites to lift your open rate.

0/300 characters

Instant score

Rated 0–100 on clarity, curiosity, urgency, and open-worthiness.

Actionable feedback

Specific improvements you can act on today.

Three rewrites

Fresh alternatives you can copy straight into your ESP.