Subject Line Generator

Produces 8–10 subject lines across five strategic approaches — each with preview text, character count, performance risk rating, and a rationale — plus A/B test pairings designed for learning, not just open-rate optimisation.

What it does

Generates subject lines across five approaches, each testing a different lever for open rate:

• Direct benefit — 2 options that explicitly state reader value
• Curiosity and intrigue — 2 options that create a genuine information gap resolved inside the email
• Specificity and numbers — 2 options using concrete figures, timeframes, or outcomes
• Question format — 2 options phrased as real audience questions
• Social proof and authority — 1–2 options leading with trust signals or evidence

Every subject line includes: approximate character count, a preview text pairing (85–100 characters), the strategic approach, a rationale, and a performance risk assessment. Lines likely to truncate on mobile are flagged — the skill targets 40–50 characters for safe mobile visibility unless truncation is strategically useful.

The output also includes two A/B test pairings, each stating the behavioural insight the test is designed to reveal — not just which line might win. A section on what to avoid lists approaches likely to hurt trust or underperform with this specific audience.

Misleading urgency, false curiosity gaps, and claims the email body doesn't support are never recommended.

When to use it

Use it before any campaign send, once you have the email topic, audience, objective, and core promise. Works best in a Claude.ai Project with persona and brand voice documents attached. Sonnet is the recommended model. For headlines on non-email content, use headline-and-hook-generator instead.

When not to use it

• For SMS or push notifications — character limits and behavioural conventions differ
• For blog, ad, or landing page headlines — use headline-and-hook-generator for those
• Without knowing the email's content — subject lines that misrepresent the body damage deliverability and list trust