Writing one subject line and hoping it works is not a strategy. This prompt generates 10 variations using different psychological triggers, so you can test two and build a subject line playbook from real data.
Your subject line determines whether anyone reads your email at all. It is the most important sentence in every broadcast and also the one most founders spend the least time on.
The standard advice is to write something curiosity-driven and keep it short. That is true but not specific enough to be useful. What actually works is having multiple approaches to choose from, testing two of them, and building a pattern library from what your specific audience responds to.
This prompt generates 10 subject line options for any email you are about to send so you always have real choices instead of settling for the first thing that came to mind.
In two to three sentences, write down what your email is about: the main topic, the key takeaway, and what you want the reader to do. This context helps Claude write subject lines that are accurate to what the reader will actually find inside the email.
Paste the prompt below along with your email summary.
Write 10 email subject lines for this broadcast: [paste your two-to-three sentence email summary]. Use a range of approaches across the 10 options: one that opens a curiosity gap, one that is ultra-specific with a number, one that uses a pattern interrupt, one that sounds like a personal message, one that names a specific problem, one that leads with the outcome, one that sounds like a secret, one that asks a question, one that challenges an assumption, and one wild card. Keep all of them under 50 characters.
Read all 10 and note which two feel most true to your content and most likely to stop a scroll. Those are your A/B test candidates. If you are not on a Kit plan with A/B testing, pick your single favorite and save the remaining options for future broadcasts.
In your Kit broadcast editor, enable A/B testing and enter your two subject lines. Set the test window based on your typical send time, generally four to six hours is enough to get statistically meaningful open rate data before the winning variant goes to the rest of your list.
After the test resolves, note which subject line won and which approach it represented: curiosity gap, specific number, pattern interrupt, and so on. Over time this log becomes your personal subject line playbook built entirely on your own audience's behavior.
Ten options and a test beats one guess every time. Run this before every broadcast and within two to three months you will have a subject line playbook your competitors cannot copy because it is built entirely on what your audience specifically responds to.
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