Back to Tools

Subject Line Tester

Optimize your open rates with our AI-powered subject line tester. Get scores on emotional impact, length, and keyword effectiveness.

AI Subject Line Analyzer

Get AI-powered feedback to boost your email open rates

Powered by Gemini
0 characters

Tips for better subject lines:

  • Keep it under 50 characters for mobile
  • Use numbers and statistics when relevant
  • Create urgency without being spammy
  • Ask a question to spark curiosity
  • Personalize with the recipient's name
  • A/B test different versions

About this tool

Your subject line is your email's first impression—it determines whether recipients open it or delete it. This tool scores your subject on proven best practices like emotional appeal, length optimization, and power words. Pair this with our preheader generator to create complementary preview text that increases click-through rates. Once you've crafted multiple variations, validate improvements using our A/B test significance calculator to ensure results are statistically real.

Frequently Asked Questions

More Free Tools

View all tools

SPF Record Generator

Generate a valid SPF record for your domain. Select your email providers, add custom IPs, and get a properly formatted TXT record ready to add to your DNS.

Email Conversion Rate Calculator

Calculate your email conversion rate, click-to-conversion rate, and revenue per email. Compare your performance against industry benchmarks for e-commerce, SaaS, and more.

Email Countdown Timer Generator

Create countdown timer HTML for your email campaigns. Choose from 3 styles, customize colors, and get email-compatible HTML. Includes guidance on making the timer live with image-based services.

Email Hook Generator

Generate attention-grabbing opening lines for your emails across 8 hook categories and 4 tones. Browse 36+ proven hooks organized by type — curiosity, urgency, story, question, statistic, contrarian, personal, and problem — then copy the perfect opener for your next campaign.