Email Subject Line Generator

Theo Williams

@theo-williams

·December 31, 2025

Create email subject lines within mobile display constraints

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Generate email subject lines within character constraints:

Email purpose: {{purpose}}
Key message: {{message}}
Audience: {{audience}}

Constraints:
- Maximum 50 characters (mobile preview)
- Ideally under 40 characters
- No spam trigger words
- Must create open-worthy curiosity
- No ALL CAPS
- Maximum 1 emoji (optional)
- Must preview well on mobile

Generate:
1. 10 subject line options
2. Character count for each
3. Preview text pairing for each
4. Mobile preview simulation
5. Spam score estimate
6. A/B test recommendations
7. Best for: Promotional/Informational/Engagement

Details

Category

Communication

Use Cases

Email marketingOpen rate optimizationMobile optimization

Works Best With

gpt-4oclaude-sonnet-4

Created December 31, 2025Updated January 19, 2026Shared December 31, 2025

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