Paste any subject line and get a real-time score, spam check, and specific tips to lift your open rate — in seconds.
Start typing to see your score
SubjectBot runs your subject through the same filters used by spam engines and real human psychology research.
We check against 40+ words that trigger spam filters — "free", "click here", "act now", "guaranteed". These silently kill deliverability.
The sweet spot is 30–60 characters. Too short = no context. Too long = mobile truncates. We score your length and tell you how to fix it.
Words like "secret", "discover", "proven", and "results" statistically increase open rates. We identify them and reward natural usage.
"7 ways to..." and "Are you making this mistake?" consistently outperform flat statements. We check for both and give credit for each.
ALL CAPS looks like shouting. Excessive !!! looks desperate. Both get flagged by spam filters. We catch both and explain the damage.
0–100 score with a letter grade, plus per-check cards with a ✅/⚠️/❌ and specific copy telling you what's wrong and what to do instead.
No account. No setup. Just type and see your score update live.
Paste or type any subject line. Scoring happens as you type — no button, no delay.
Get an instant 0–100 score with a grade and a visual breakdown of every check that passed or failed.
Each failed check explains exactly what to change and why. No vague advice — specific, actionable guidance.
Edit your subject and watch the score update. Keep going until you hit Excellent (80+) before you hit send.
Everything you need to know about SubjectBot.
We're building a full email scheduler with built-in subject scoring and A/B testing. Be first in line.
No spam. One email when we launch.
Free tools for creators, marketers, and founders. No account needed.