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Enter a Subject Line
Type or paste your email subject line above to get instant analysis on length, spam triggers, and emotional engagement.
About Email Subject Line Tester
Test and optimize your email subject lines with our free online analyzer. Get instant feedback on subject line length (optimal 30-50 characters), detect spam trigger words that could hurt deliverability, and measure emotional engagement score based on power words, urgency, personalization, and more. See an overall score with detailed breakdowns and actionable suggestions to improve your email open rates. Perfect for marketers, sales teams, and anyone sending email campaigns. All processing happens locally in your browser - your subject lines never leave your device.
What This Tool Analyzes
Length Analysis
Optimal subject lines are 30-50 characters. Too short lacks context; too long gets cut off on mobile devices.
Spam Detection
Identifies words that trigger spam filters like "free", "urgent", "winner" and suggests alternatives.
Emotional Score
Measures engagement potential based on power words, personalization, questions, and urgency.
Email Subject Line Best Practices
- Keep it concise: 30-50 characters display fully on most devices
- Create urgency: Use time-sensitive language when appropriate
- Personalize: Include "you" or "your" to increase relevance
- Be specific: Numbers and statistics boost credibility
- Ask questions: Questions engage readers and spark curiosity
- Avoid spam triggers: Words like "free", "winner", "act now" hurt deliverability
- Skip ALL CAPS: It looks like shouting and triggers spam filters
Understanding the Score
Frequently Asked Questions
What is the ideal email subject line length?
The ideal email subject line length is 30-50 characters. This range ensures your subject displays fully on most email clients, including mobile devices. Subject lines under 20 characters may lack context, while those over 60 characters often get cut off.
What are spam trigger words?
Spam trigger words are terms commonly associated with unwanted emails that can cause email filters to mark your message as spam. High-risk words include "free", "winner", "congratulations", "urgent", "act now", and "limited time".
What is the emotional score?
The emotional score measures how engaging and compelling your subject line is likely to be. It analyzes power words, urgency indicators, personalization (you, your), questions, numbers for specificity, and emoji usage.
How is the overall score calculated?
The overall score is a weighted combination of three factors: length score (30%), spam score (35%), and emotional engagement score (35%). Higher scores indicate better subject lines that are more likely to be opened.
Is my subject line data safe?
Yes! All analysis happens entirely in your browser using JavaScript. Your email subject lines are never sent to any server, ensuring complete privacy for your marketing content.