AI Email Subject Line Generator

Email Subject Line Best Practices

• Keep it under 50 characters — 82% of top-performing subject lines are under 50 characters. Mobile screens cut off anything longer.
• Use numbers when relevant — "5 ways to..." outperforms "Ways to..." by 36% on average.
• Create a curiosity gap — tell them enough to be intrigued, not enough to satisfy their curiosity without opening.
• Personalize when possible — subject lines with the recipient's name get 22% higher open rates.
• Avoid spam triggers — words like "FREE!!!", "Act now!!!", and excessive caps/punctuation hurt deliverability.
• A/B test religiously — send two variants to 10% of your list each, then send the winner to the remaining 80%.
• Match the subject to the content — clickbait subject lines destroy trust and increase unsubscribes.