Free Email Subject Line Tester
Score an email subject line for clarity, length, mobile visibility, specificity, capitalization, punctuation, risky phrasing and preview-text alignment.
Rules-first email checker
Local scoringAnalyze Your Subject Line
Get an explainable score, detailed checks and three optional AI rewrites.
Subject line score
How to Improve an Email Subject Line
Use the score to find clear mechanical issues, then judge the final line against your audience, offer and brand. A high score cannot guarantee opens.
Pair subject and preview text
The preview should extend the idea instead of repeating it. For fresh campaign angles, use the AI Email Subject Line Generator.