Craft irresistible subject lines that drive opens
Receive instant optimization suggestions and performance insights as you create each subject line.
Research-backed optimization criteria
Our subject line analyzer evaluates your content against proven best practices and industry data. Each assessment is based on comprehensive research to maximize your email open rates:
Optimal Length
Mobile users see only the first 30 characters of subject lines. We help you prioritize your key message within this critical character limit for maximum visibility.
Readability Score
We analyze readability using proven metrics to ensure your subject lines are instantly understood by recipients scanning their inbox quickly.
High-Impact Keywords
Our analysis identifies engagement-boosting keywords that correlate with higher open rates. We'll highlight when your subject line includes these powerful terms.
Spam Trigger Detection
We identify problematic words and phrases that commonly trigger spam filters or reduce engagement. Our system alerts you to these risks before you send.
Smart Formatting
We evaluate capitalization patterns to prevent spam filter triggers while optimizing for your audience's preferences and response patterns.
Numerical Elements
Research demonstrates that incorporating numbers in subject lines can significantly boost open rates by adding specificity and urgency.