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Free Tool
Email Subject Scorer
Improve your open rates. Check for spam triggers and power words instantly.
Draft Subject
Try testing 3 different variations to see which scores highest.
Analysis
Enter a subject line to analyze.
A/B Test Live?
Don't guess. KDP Sentinel Pro integrates with your newsletter to run live A/B tests.
Start TestingInbox Mastery
What is a good open rate?
For authors, 40-50% is excellent. 20-30% is average. Below 20% means you need to clean your list or fix your subject lines.
Why avoid 'free'?
Spam filters hate it. Use 'Gift', 'Complimentary', or 'Zero Cost' instead to avoid the Promotions tab.
Audience Growth
Own Your Audience.
Upgrade to KDP Sentinel Pro for automated sequence templates and list cleaning tools.
Upgrade to KDP Sentinel Pro