Free Email Marketing Tool

Email A/B Subject Line Tester

Compare 2–10 email subject lines with advanced scoring, spam-risk detection, inbox preview, personalization checks, and A/B testing recommendations.

Accuracy note: This tool provides rule-based marketing analysis, not guaranteed open-rate prediction. Use it to avoid obvious issues, compare quality, and choose better A/B test candidates.
Variants
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Best score
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Avg score
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Spam risk
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Best variant
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1. Add Subject Line Variants

Enter one subject per line. Add preview text if you want inbox preview scoring.

2. Comparison Results

Score combines length, clarity, spam risk, formatting, personalization, preview fit, and campaign type.

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Variant Subject Score Grade Chars Words Spam Emoji Recommendation Action
No analysis yet.

Winner Summary

Run analysis to see the recommended A/B winner.

Inbox Preview

Desktop preview
Winner subject will appear here
Preview text will appear here
Mobile preview
Winner subject will appear here
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A/B Testing Tip

If top two scores are close, test both. A rule-based score helps reduce avoidable issues, but real audience behavior should decide final winners.

Detailed Feedback

About Email A/B Subject Line Tester

Email A/B Subject Line Tester helps marketers compare subject line variants before sending campaigns. It checks multiple factors that often affect deliverability perception, inbox readability, and testing quality.

Common use cases

  • Compare 2–10 subject lines before newsletter or promotional campaigns.
  • Find spam-heavy or over-promotional subject lines before sending.
  • Select safer A/B test candidates for cold outreach and sales campaigns.
  • Create a downloadable comparison report for marketing teams.