Score any email subject line across 6 dimensions: length, personalization, spam risk, numbers, curiosity, and punctuation. Get an instant grade and improvement tips.
What it does
Scores your email subject lines across multiple dimensions — length, power words, personalization, emotional triggers, and spam risk — to predict open rate performance.
Why it matters
35% of recipients decide to open an email based solely on the subject line. A well-tested subject line can increase campaign performance by 2-3x.
Definition
Subject line testing evaluates the predicted effectiveness of an email subject line using factors like word count, emotional tone, clarity, urgency, and spam trigger analysis.
Assumptions
How to interpret your results
Aim for scores above 75. Subject lines scoring below 50 should be rewritten. The most impactful improvements are usually reducing length and adding a specific number or name.
How to improve
Keep it under 50 characters
Mobile devices truncate at 40-50 characters — front-load your key message
Use preview text strategically
The preview text is your second subject line — don't waste it
Test against your best performers
Beat your current champion before sending to the full list