Email Subject Line Tester

Score your email subject line on length, urgency, personalization, spam trigger words, and predicted open rate.

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How it works

This tool evaluates your email subject line across five key dimensions used by email marketing professionals. All analysis runs entirely in your browser.

• Length: evaluates character and word count. Research shows subject lines between 30–60 characters (6–10 words) achieve the highest open rates. Shorter lines display fully on mobile devices, while overly long ones get truncated.
• Urgency: detects time-sensitive language such as “now,” “today,” “limited time,” and “expires.” Moderate urgency drives action, but excessive urgency can feel spammy. The ideal subject line includes 1–2 urgency cues.
• Personalization: checks for personalization tokens like names, “you/your,” and segmentation cues. Personalized subject lines can increase open rates by 20–30% compared to generic ones.
• Spam Trigger Words: scans for words and phrases commonly flagged by spam filters, such as “free,” “act now,” “guarantee,” and “no obligation.” Fewer spam triggers means better deliverability.
• Open Rate Prediction: combines all dimension scores with additional signals (emoji use, question marks, numbers, capitalization) to estimate a relative open rate. This is a heuristic based on industry benchmarks, not a guarantee.

The overall score is a weighted average of all dimensions on a 0–100 scale. Scores above 70 indicate a well-optimized subject line.

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