Email Subject Line Generator

How to Write Email Subject Lines That Get Opened

Your email subject line is the most important part of your email. It doesn't matter how good your content is if nobody opens it. The average open rate across industries is just 21% — meaning 4 out of 5 people never see your message.

What Makes a Great Subject Line?

1. Curiosity gap. Hint at something without revealing everything. "You won't believe what we just added..." works because humans are wired to close information gaps.

2. Personalization. Including the recipient's name or a reference to their behavior ("You left something behind...") can boost open rates by 26%.

3. Numbers. Specific numbers feel credible. "5 ways to..." outperforms "ways to..." every time.

4. Urgency. "Last chance," "ends tonight," and "only 3 left" create FOMO. Use sparingly or it loses effect.

5. Length. Keep it under 50 characters for mobile. Over 60 and it gets cut off on most devices.

The 5 Subject Line Styles We Generate

Urgent: Creates time pressure ("Offer ends in 6 hours")

Curious: Opens a loop ("The mistake 90% of store owners make")

Friendly: Warm and conversational ("Hey — we saved something for you")

Professional: Clear and value-focused ("Your Q1 marketing checklist is ready")

Playful: Fun and memorable ("We may have gone overboard with the deals 🎉")

A/B Testing Your Subject Lines

Always test at least two subject lines when you can. Send variation A to 20% of your list and variation B to another 20%. Wait 4 hours. Send the winner to the remaining 60%.

SnapCopyAI generates 5 variations at once — perfect for split testing.