Paste one email subject line. Get a 0–100 open-probability score across length, spam-triggers, specificity, curiosity and formatting — plus the exact fixes. Runs in your browser, no signup, nothing stored.
100% client-side · deterministic heuristics · your text never leaves the page. This estimates open-signal from documented email-marketing rules — it is not a guarantee of open rate.
These are the moves high-open subject lines make. Two ways to get there:
More free tools → Cold Email Grader · Headline Tester · Landing Page Grader
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