Free Subject Line Tester.
Improve your open rates today.
Get an instant score out of 100, AI-powered rewrites, spam trigger checks, and open rate estimates.
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Learn MoreFrom subject line
to campaign in minutes
No setup. No credit card. Paste your subject line, get your score, and send better emails — free.
Enter your email subject line
Type or paste any subject line — promotional, newsletter, transactional, re-engagement. Works for every email type.
Get your subject line score instantly
Our AI analyzes 40+ signals — length, language, emotion, urgency, spam risk — then gives you a score out of 100 with a plain-English breakdown.
Improve & launch
Get AI-powered rewrite suggestions, turn your subject line into a full email campaign, and send it directly with Constant Contact.
Your account saves everything automatically
Score history, trends, project workspaces — all organized, all free.
Built for email marketers
who care about results
Subject line scoring, deliverability checker, open rate predictor, AI rewrites, all in one tool.
Subject Line Score (0–100)
Instant 0–100 rating based on engagement signals, deliverability risk, word power, and emotional resonance — with a plain-English breakdown.
AI Subject Line Rewriter
5 AI-generated alternatives — shorter, more emotional, urgency-driven, or curiosity-based — each graded so you can pick the best one instantly.
Open Rate Predictor PRO
See your predicted open rate range before you hit send. Calibrated against real benchmark data for your specific industry.
Industry Benchmarks PRO
Compare your predicted open rate with other marketers in your industry. Know exactly where you stand.
Projects & History PRO
Every subject line is saved. Organize by project, view trends over 30/90/all-time, and spot your winning patterns.
AI Email Builder
Love your subject line? Send it straight to Constant Contact's AI Email Builder — it'll craft a full campaign around it, ready for you to personalize and send.
Start free.
Upgrade when you're ready.
Start scoring subject lines for free today. Upgrade to Pro for open rate predictions, industry benchmarks, and full history.
Free
Everything you need to start writing better subject lines today.
- ✓ Unlimited subject line scoring
- ✓ AI rewrite suggestions (9 per score)
- ✓ Score history – last 30 days
- ✓ Basic dashboard & trends
Pro
Billed annually · Cancel anytime
For marketers serious about performance, open rates, and benchmarks.
- ✓ Everything in Free
- ✓ Predicted Open Rate
- ✓ Industry benchmark comparison
- ✓ Unlimited Projects
- ✓ Score history – Lifetime
Cancel anytime · Secure payment · Instant access
Ready to boost
your open rates?
Create your free account and save your history, get AI rewrites, and unlock open rate predictions & industry benchmarks.