Subject Line Generator
/subject-lines
Claude Code produces subject line variants across multiple psychological angles including curiosity, specificity, urgency, and social proof, paired with preview text that completes the open invitation. Each batch is organized by type so you can pick and test across your list.
What this skill does
Generate subject line variants across 5 to 6 psychological angles for the same email campaign
Write preview text that pairs with each subject line to maximize the combined open rate
Flag subject lines likely to trigger spam filters based on common trigger words
Produce A/B test pairs matched by angle type for statistically clean tests
How to use it
Describe the email campaign
Share what the email is about, the subscriber segment, and the primary goal (open and click, open only, or direct purchase).
Run /subject-lines
Specify how many variants you want and whether you need preview text included with each subject line.
Test and track
Load the top 2 to 3 variants into your A/B test and track open rates and click-through rates separately.
Example prompts
$Write 10 subject line and preview text pairs for a newsletter about Q1 Google Ads trends. Audience: e-commerce marketing managers.
$Generate 8 subject lines for a promotional email with a 24-hour flash sale. Product: $79 marketing template pack. No misleading urgency.
$Create subject line variants for a cold email campaign to SaaS founders about our marketing analytics tool. Focus on curiosity and specificity angles.
Who it's for
Email marketers running weekly newsletters who need subject line options to test each send
E-commerce brands sending promotional campaigns who want to maximize open rates
B2B teams running cold email campaigns at scale who need personalization-friendly subject lines
Frequently asked questions
Does subject line length matter?
Most email clients display 40 to 50 characters before truncating on mobile. Claude Code writes subjects within 45 characters by default. Longer subject lines can work when the first 45 characters create enough curiosity to make the truncation feel intentional.
What subject line types get the highest open rates?
Specificity and curiosity consistently outperform generic promotional language. Subject lines that reference the reader's specific situation or use a specific number tend to beat vague benefit statements. Claude Code generates multiple types so you can test which performs best with your specific audience.
How do I avoid my subject lines triggering spam filters?
Avoid ALL CAPS, excessive punctuation, and trigger words like 'free', 'guaranteed', and 'urgent'. Claude Code flags likely spam triggers in generated subjects and suggests cleaner alternatives that maintain the same psychological angle.
Skills that pair well
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