Email Subject Line Tester
By CopyJumpTest how your email subject lines appear across different email clients and get copywriting insights
Your subject line is the first thing subscribers see. This tool helps you:
- Preview subject lines across Gmail, Outlook, Apple Mail, and more
- See character limits and truncation points for each client
- Get instant copywriting technique analysis and scoring
- Discover optimization opportunities for better open rates
Copywriting Technique Examples
Click on a technique below to see examples you can use for inspiration:
Email Subject Line Best Practices
Optimal Length Guidelines
Different email clients display different amounts of subject line text:
- Gmail Desktop: ~60 characters (longer subject lines work well)
- Gmail Mobile: ~30 characters (keep it short and punchy)
- Outlook: ~50 characters (balanced approach)
- Apple Mail Mobile: ~35 characters (similar to Gmail mobile)
High-Performing Copywriting Techniques
Curiosity Gaps:
- • "The mistake costing you 50% of sales"
- • "Why your best customers leave"
- • "What 97% of marketers get wrong"
Numbers & Specificity:
- • "3 words that increased opens 127%"
- • "47% of subscribers do this tomorrow"
- • "How I made $12,847 in 3 days"
What to Avoid
- Excessive use of ALL CAPS (triggers spam filters)
- Too many special characters or emojis
- Spam trigger words like "free," "guaranteed," "act now"
- Generic subject lines like "Newsletter #47"
- Misleading or clickbait subject lines that don't match content
Mobile Optimization Strategy
📱 Front-Load Important Words
Put your most compelling words at the beginning since mobile displays are limited to ~30 characters.
⚡ Create Urgency Early
Use time-sensitive words like "Today," "Now," or "Ending" at the start of your subject line.
🎯 Test Both Lengths
Create short versions for mobile impact and longer versions for desktop context.
📊 Track Performance
A/B test different subject line approaches and track open rates across devices.
Advanced Subject Line Strategies
🧠 Psychological Triggers
Use curiosity, urgency, social proof, and personalization to create emotional responses that drive opens.
📝 Personalization Beyond Names
Reference recent behavior, purchase history, or location instead of just using first names.
❓ Question-Based Subject Lines
Questions create mental loops that subscribers want to close by opening your email.
📈 Segmentation Strategy
Create different subject lines for different subscriber segments based on their interests and behavior.
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