🔍 Subject Line Analyzer
Paste a cold email subject line and get an instant AI breakdown — length, action verb, personalisation, spam triggers, clarity — plus three rewritten alternatives.
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Analysis
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Paste a subject line and click Analyze
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Frequently asked questions
What does the analyzer actually check?+
Character length (mobile-clipping risk), word count, action-verb presence, personalisation markers (first name, company, role), spam-trigger phrases ("guarantee", "free", excessive punctuation), urgency tone, and overall clarity. Each dimension gets a score and a one-line explanation.
Why do shorter subject lines convert better?+
Gmail truncates at ~50 characters on desktop and ~30 on mobile. Subject lines longer than the truncation window force the reader to fill in the missing words — most don't bother. Top-performing cold subject lines in 2026 sit in the 25–45 character range.
Does it work for non-cold use cases (nurture, broadcast)?+
Yes. The same readability and clarity principles apply. The spam-trigger dictionary is tuned for B2B sales outbound, so warm broadcasts (e.g. existing customer comms) will score lower-risk on spam by default.
How are the rewritten alternatives generated?+
Claude produces three variants — one shorter and punchier, one with a curiosity hook, one with explicit personalisation — using the same context you supply (industry, persona, what your product does). Then it explains the trade-offs of each so you can pick.
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