Free Tool
Paste any subject line. Get an instant score, 6-dimension breakdown, and three specific improvements — no signup required.
Type or paste any subject line — marketing email, newsletter, cold outreach, whatever you're writing.
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Most email subject lines fail for the same handful of reasons: they're too vague, they trigger spam filters, or they give away the whole story instead of creating curiosity. This tool scores against six dimensions that actually correlate with open rates.
The single biggest lever? Curiosity and urgency. A subject line needs a reason to be opened now. A question, a number, a specific claim, a tension — something that creates an open loop the reader's brain wants to close.
Mobile email clients (where 60%+ of opens happen) clip subject lines around 40–50 chars. Gmail shows ~70 on desktop. Write for mobile first.
Subject lines with the recipient's name or "you/your" language outperform generic ones by ~26% on average. The reader cares about their problems, not yours.
A question creates an open loop — the brain is wired to want answers. "Why most marketers get this wrong" beats "Tips for email marketing" every time.
A single, relevant emoji at the start or end of a subject line can lift open rates 5–15%. Two or more start to look like spam. Zero is also fine — especially for B2B.