Email Subject Line Tester & Scorer
Score any email subject line for open-rate potential, spam risk, and length, then get 8 stronger rewrites.
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Test any email subject line in seconds and see exactly why it will, or won't, get opened. This free email subject line tester scores your line 0-100 for open-rate potential, spam-trigger risk, length, and emotional tone, then hands you 8 stronger rewrites grouped by angle. Perfect for email marketers, newsletter operators, and growth teams who want higher open rates without guessing.
How to use the Email Subject Line Tester & Scorer
- Enter your subject line.
- Enter your email purpose / campaign type.
- Enter your audience.
- Click Generate and copy your result.
Frequently asked questions
How is the email subject line score calculated?
The tool scores your subject line 0-100 based on open-rate drivers like curiosity, clarity, specificity, personalization, and urgency, combined with deliverability factors such as spam-trigger words, length, and mobile truncation. You get a breakdown card showing open-rate potential, spam risk, length, emotion, and clarity so you know exactly what to fix.
What makes an email subject line land in spam?
Common spam triggers include words like 'free', 'guaranteed', 'act now', and '$$$', ALL CAPS, excessive punctuation (!!!), and misleading clickbait. The tester flags the specific triggers in your line and rates spam risk Low, Medium, or High so you can clean it up before sending.
What is the ideal email subject line length?
Aim for roughly 30-50 characters or 4-7 words. Many inboxes, especially on mobile, truncate subject lines around 30-40 characters, so front-load the most important words. The tool reports your exact character and word count and flags lines that risk being cut off.
Will the rewrites work for any campaign type?
Yes. You can optionally set your campaign type (newsletter, promotion, cold outreach, re-engagement, and more) and audience, and the 8 ranked rewrites are tailored to fit. They span varied angles, curiosity, urgency, value, personalized, question, and short-and-punchy, so you can A/B test different approaches.