How to write email subject lines that get opened

Executive overview

Most email subject line advice sounds definitive but isn't. What actually works depends on your audience and their environment — there are no universal rules, only variables worth testing.

The job of a subject line is to answer two questions: why open, and why now. Everything else — length, tone, format — is secondary to whether you trigger an emotional response.

The core insight: people open emails because of emotion, not logic — write to the lizard brain, not the inbox scanner.

The five things to keep in mind

• Elicit emotion first: curiosity, urgency, relevance, trust, instant gratification, fear, or authority
• Answer "why open" and "why now" — these are the only two impulses that matter
• Communicate at a deeper, subconscious level using six drivers: self-centeredness, contrast, tangibility, narrative arc, visual stimuli, emotion
• Match the tone of a friend, not a corporation — formal feels like work, casual gets clicks
• Source subject lines from your audience's own language, not from guesswork

On length

• Length doesn't matter — what matters is how many words it takes to trigger a response
• Short (one word), medium, and long can all work; test each against your list
• "Hey" as a subject line works because it creates curiosity and feels personal

Where to find subject line inspiration

• Subreddits in your niche — look at post titles with high comment counts
• Google Suggest — type keywords and observe what autocompletes
• popurls.com — curates trending headlines across topics
• Amazon book titles and reviews — short, punchy, audience-sourced language