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Back to Prompt Library
Marketing
Email MarketingCopywritingTesting

Email Subject Line Generator and Optimizer

Generates 20 subject lines across 5 psychological categories, with a top-3 recommendation.

Best For

  • •An email marketer prepping a product launch send uses it to generate a real A/B test set across 5 psychological angles instead of guessing two variants
  • •A newsletter writer with declining open rates uses the curiosity-gap and question-format categories to break out of a stale pattern
  • •A growth marketer reporting on subject line performance uses the 'why it works' annotations to explain test results to stakeholders

Prompt Template

Generate 20 email subject lines for [EMAIL PURPOSE, newsletter issue / product launch / re-engagement / cold outreach]. Email content summary: [1–2 SENTENCE SUMMARY]. Audience: [AUDIENCE]. Goal metric: [OPEN RATE / REPLY RATE / CLICK RATE]. Deliver 4 subject lines in each of these 5 categories: (1) Curiosity gap ('You're making this mistake every day'), (2) Direct benefit ('Double your open rates in 7 days'), (3) Question format ('Are you leaving 40% of your revenue on the table?'), (4) Social proof ('How [NAME/BRAND] achieved [RESULT]'), (5) Urgency or scarcity. For each subject line, add a 'Why it works' annotation of one sentence. Flag your top 3 picks and explain why.

Pro Tip

Test winners against your own historical open-rate data rather than trusting the model's top-3 picks blindly, since subject line performance is highly audience-specific.

Example Output

A sample of what this prompt produces once you fill in the placeholders.

Curiosity: 'The metric everyone tracks wrong.' Direct benefit: 'Cut your reporting time by half this week.' Why it works: names a specific pain your audience already recognizes without revealing the answer.

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How to use this prompt

  1. Copy the prompt template using the button above.
  2. Paste it into your preferred AI assistant (ChatGPT, Claude, Gemini, etc.).
  3. Replace all bracketed placeholders like [TOPIC] with your specific details.
  4. Send the prompt and refine the output as needed.

Related

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