The subject line is the single most important part of an email — it decides whether the email gets opened at all. You can write the perfect message, but if the subject doesn’t earn the click, no one reads it. Here’s how to write subject lines that get opened.
Be clear before clever
Clarity beats cleverness almost every time. The reader should know what the email is about and why it matters to them. A vague-but-witty subject loses to a plain-but-clear one: “Invoice #204 — due Friday” beats “A little something for you 👀”.
Be specific
Specificity signals relevance and value. “Quick question about your order” is okay; “Quick question about your order #204” is better. Numbers, names, and concrete details earn opens.
Front-load the important words
Inboxes — especially on mobile — cut subject lines off after a few words. Put the key information first so it survives the truncation. Aim for around 6–10 words.
Match the subject to the email
Never overpromise to win an open — a misleading subject gets your email opened once and trusted never again. The subject is a promise; the body must keep it. This honesty also keeps you out of spam folders.
Tailor the tone
A subject line for a job application, a newsletter, and a reminder to a friend should sound different. When you’ve drafted one but it’s not landing, the paraphraser gives you variants in different tones — and the title generator is great for brainstorming punchy angles to react to.
Avoid the spam triggers
ALL CAPS, excessive punctuation (!!!), and words like “free,” “guaranteed,” and “act now” trip spam filters and erode trust. Write like a person, not a billboard.
Test and learn
If you send at volume (newsletters, campaigns), try two subject lines on a small split and send the winner to the rest. Over time you’ll learn what your specific audience opens.
A quick checklist
- Clear about what’s inside? ✓
- Specific, not generic? ✓
- Important words first? ✓
- Honest — matches the body? ✓
- Free of spam triggers and typos? Run it through the grammar checker. ✓
Clear, specific, honest, and front-loaded — that’s a subject line that earns the open and keeps the trust.
AI-powered — please review results before use.