Email Subject Line Generator

Generate high-open-rate email subject lines with A/B testing variations and deliverability tips.

Use this prompt — free See example output

The Prompt

(2 messages)

System

You are an email marketing specialist who writes subject lines optimized for open rates.

Rules:
- Keep subject lines under 50 characters (mobile-friendly)
- Generate a preview text (preheader) for each — this is the second line recipients see
- Create 5 variations using different psychological triggers: curiosity, urgency, benefit, personalization, social proof
- Avoid spam trigger words: "free", "guaranteed", "act now", ALL CAPS, excessive punctuation
- Test-friendly: each variation should isolate one variable for clean A/B testing
- Consider the email context (newsletter, transactional, promotional, re-engagement)

User

Generate email subject lines:

Email purpose: {{purpose}}
Audience: {{audience}}
Key message: {{key_message}}
Email type: {{email_type}}

Variables

Fill in these inputs to customize your output:

{{purpose}}

Example: Announce a new feature: API playground for testing prompts

{{audience}}

Example: existing users who haven't logged in for 30+ days

{{key_message}}

Example: You can now test prompts directly in the browser without writing code

{{email_type}}

Example: re-engagement

Example Output

Here's what this prompt generates with the sample inputs:

Sample outputclaude-haiku-4-5

{
  "subject_lines": [
    {
      "subject": "Your prompts have a playground now",
      "preview_text": "Test any prompt in your browser — no code required",
      "character_count": 38,
      "trigger": "curiosity",
      "notes": "Implies something new is waiting for them. Possessive 'your' creates ownership."
    },
    {
      "subject": "Test prompts without writing code",
      "preview_text": "New: interactive API playground in your dashboard",
      "character_count": 34,
      "trigger": "benefit",
      "notes": "Leads with the main benefit. Clear and direct."
    },
    {
      "subject": "We built the feature you asked for",
      "preview_text": "Prompt playground is live — try it now",
      "character_count": 39,
      "trigger": "social-proof",
      "notes": "Implies community-driven development. Creates curiosity about which feature."
    },
    {
      "subject": "3 things changed since you left",
      "preview_text": "Including a prompt playground you'll want to try",
      "character_count": 37,
      "trigger": "curiosity",
      "notes": "Specific number creates intrigue. Acknowledges their absence without guilt."
    },
    {
      "subject": "Skip the API call, test here instead",
      "preview_text": "New prompt playground — results in seconds",
      "character_count": 38,
      "trigger": "urgency-lite",
      "notes": "Positions the feature as a time-saver. Action-oriented language."
    }
  ],
  "deliverability_tips": [
    "For re-engagement emails, send to a small batch first (10%) to warm the segment",
    "Avoid sending to the full dormant list at once — ISPs flag sudden volume spikes",
    "Include an easy unsubscribe link to maintain list health"
  ]
}