Instant5 free tests/day · Unlimited with $79/month Pro
Email Subject Line Tester
Score your subject line in real time — spam risk, personalization, power words, emoji, and open rate estimate. No AI, no waiting.
How it works
Scores email subject lines across 7 dimensions using deterministic rules — no AI, instant results. Checks length (35-50 chars is optimal), spam words, power words, personalization signals, question format, emoji usage, and number inclusion. Also generates 3 alternative subject lines and estimates open rate based on aggregate benchmarks.
What you get
- ✓Score out of 100 with letter grade
- ✓Estimated open rate range based on score
- ✓7-dimension breakdown with specific feedback
- ✓Spam word detection with list of flagged words
- ✓3 alternative subject lines you can use immediately
0 characters