Prompt: Generate Subject Line A/B Test Variants
For Email Marketing Specialists
Level 1 — Free chatbot (ChatGPT or Claude) | Time: 2-3 minutes
The Prompt
Write 10 subject line options for the following email:
Email topic: [describe what the email is about in 1-2 sentences]
Key offer or message: [discount, announcement, content, etc.]
Target audience: [who's receiving this — demographics, behavior, relationship to brand]
Brand tone: [formal / casual / playful / authoritative]
Average open rate we're trying to beat: [your current open rate, e.g., "22%"]
Generate one subject line for each of these angles:
1. Direct / plain language
2. Urgency / time pressure
3. Benefit-first ("What's in it for me")
4. Curiosity / open loop
5. FOMO / social proof
6. Question format
7. Personalization angle (e.g., referencing behavior or segment)
8. Humor or wordplay
9. Short (under 30 characters)
10. Long (over 50 characters, adds detail)
For each, estimate: (a) predicted open rate vs. our baseline, (b) best audience match, (c) any risk or downside.
How to Use This
Use this prompt before every campaign send, not just when you're stuck. Even if you already have a subject line you like, running this comparison surfaces angles you didn't consider and creates a ready-made A/B test.
After getting the output:
- Pick 2-3 for actual A/B testing — choose ones from different angle categories for maximum learning
- Discard any that don't match your brand voice before testing
- Note which angles perform best over time — this tells you what your specific audience responds to
Use the AI's risk assessments — they'll flag subject lines that might trigger spam filters (excessive caps, punctuation) or that misrepresent the email content.
Example
Input:
Email topic: Announcing a new integration between our project management tool and Slack
Key offer: Free for all existing customers
Audience: Active users who log in at least weekly
Brand tone: Professional but conversational — we're a team tool, not enterprise software
Open rate to beat: 28%
What good output looks like:
- Direct: "New: Slack integration is live"
- Urgency: "Your Slack integration is ready — set it up today"
- Benefit: "Stop copy-pasting between tools. Slack is here."
- Curiosity: "Something new just showed up in your account"
- FOMO: "1,200 teams already set this up this week"
- Question: "How much time do you spend copy-pasting into Slack?"
- Personalization: "For power users: your new Slack integration"
- Humor: "We heard you liked notifications, so we put notifications in your notifications"
- Short: "Slack is here"
- Long: "Your project management tool now talks directly to Slack — here's how to connect them"
Variations
For e-commerce seasonal campaigns:
Add: "Note: This is for a Black Friday sale. Include angles that feel different from the 30+ other Black Friday emails subscribers are getting that week."
For re-engagement emails specifically:
Add: "Note: These subscribers haven't opened in 90 days. Subject lines should feel personal and low-pressure, not promotional. We want them to open out of curiosity or connection, not urgency."
For B2B nurture sequences:
Add: "Note: This is email 4 of a 7-email nurture. The audience knows who we are but hasn't converted. Subject lines should feel like a helpful follow-up, not a push."
Works with: ChatGPT (free), Claude (free), Gemini (free)