Generate High-Converting
Email Subject Lines
with AI
Boost your email open rates with AI-powered subject lines. Get 10+ variations instantly, optimized for engagement, clarity, and conversion.
Example AI-Generated Subject Lines
52 characters • FOMO + Urgency
37 characters • Curiosity-driven
48 characters • Benefit-focused
42 characters • Personalized
Why SubjectLine Pro?
AI-powered tools to craft subject lines that get opened, clicked, and convert.
AI-Powered Generation
Generate 10+ high-quality subject line variations in seconds using AI (via Vercel AI Gateway). Each one optimized for engagement and conversion.
Effectiveness Scoring
Every subject line gets a 1-10 effectiveness score with power word analysis and best practice recommendations.
50+ Email Templates
Pre-written professional email templates for cold outreach, marketing, customer service, and job search scenarios.
Subject Line Optimizer
Analyze existing subject lines for character count, power words, spam triggers, and get actionable improvement suggestions.
Share & History
Save your favorites to browser history, share results via URL, and export to CSV. All data stays private in your browser.
Industry-Specific
Tailored suggestions for B2B SaaS, e-commerce, real estate, healthcare, finance, and more. Best practices built in.
Complete Email Subject Line Toolkit
🎯 Subject Line Generator
Generate 10+ subject line variations tailored to your email purpose, audience, and tone. Choose from professional, friendly, urgent, or persuasive styles.
Start Generating →⚡ Subject Line Optimizer
Analyze your existing subject lines for character count, power words, spam triggers, and get AI-powered improvement suggestions.
Optimize Now →📚 Email Template Library
Browse 50+ professional email templates with subject line variations. Categories include cold outreach, marketing, customer service, and job search.
Browse Templates →💾 History & Favorites
All your generations are saved locally in your browser. View history, save favorites, and export to CSV. No account needed, complete privacy.
View History →Complete Your Email Workflow
Explore our suite of AI-powered email tools to craft professional emails from start to finish.
Your Privacy Matters
Local Storage Only: All your generations and history stay in your browser. No server storage of your content.
No Account Required: Start generating immediately. No registration, no email collection.
Full Control: Export your history to CSV anytime. Clear your data whenever you want.
Frequently Asked Questions
Everything you need to know about SubjectLine Pro
How does the AI subject line generator work?
SubjectLine Pro uses AI (via Vercel AI Gateway with the gpt-5-nano model) to analyze your email purpose, target audience, and desired tone. It generates 10+ unique subject line variations optimized for engagement, clarity, and conversion. Each subject line is scored on effectiveness (1-10) and includes power word analysis.
Is my data private and secure?
Yes! All your generated subject lines and history are stored locally in your browser using IndexedDB. We never store your content on our servers. When you use AI features, only the minimal information needed for generation is sent to our AI provider. No account or email is required.
What makes a good email subject line?
Great subject lines are 40-60 characters, create curiosity or urgency, use power words, avoid spam triggers, and are personalized when possible. They should clearly indicate the email's value while being compelling enough to get opened. Our optimizer analyzes all these factors and provides actionable recommendations.
Can I use these subject lines commercially?
Absolutely! All generated subject lines are yours to use freely in any commercial or personal email campaigns. There are no restrictions or attribution requirements. Use them for marketing emails, sales outreach, newsletters, or any other purpose.
How do I A/B test my subject lines?
Use our A/B Testing Recommender tool to compare 2-3 subject lines side by side. The tool analyzes each variant's strengths and weaknesses, providing recommendations on which to test first and what metrics to track. Export your top candidates and run split tests in your email platform to find the winner.
Do you have email templates I can use?
Yes! Our template library includes 50+ professional email templates for cold outreach, marketing campaigns, customer service, and job search scenarios. Each template includes multiple subject line variations and can be customized with AI to match your specific needs.
What industries work best with SubjectLine Pro?
SubjectLine Pro is designed for all industries including B2B SaaS, e-commerce, real estate, healthcare, finance, education, and more. Our AI understands industry-specific best practices and can generate subject lines tailored to your sector's unique communication style and compliance requirements.
How can I share my subject line results?
Click the 'Share Results' button after generating subject lines. This creates a unique URL that encodes all your results, allowing you to share them with team members or save them for later. You can also export your history to CSV format for reporting and analysis.
Ready to Boost Your Email Open Rates?
Join thousands of marketers, sales teams, and professionals using SubjectLine Pro to craft compelling email subject lines.
Generate Your First Subject Line →