Share on:
Why users choose our AI Subject Line Generator
| 💡 Guests | up to 1000 characters, the response can contain a maximum of 1000 tokens |
|---|---|
| 🪙 Users | up to 1500 characters, maximum response size 1500 tokens |
| 🎯 PRO version | up to 32000 characters per send, the response can contain a maximum of 32000 characters, ad-free, and a separate queue |
AI Email Subject Line Generator
Effortlessly craft catchy, professional, and customized email subject lines that boost open rates. This free AI tool turns your context and style into on-brand subject ideas optimized for clarity, curiosity, and clicks.
How to use
- Select your language to match your audience.
- Paste the email context: offer, value prop, audience, CTA, campaign goal.
- Choose a style: friendly, professional, urgent, witty, educational, etc.
- Set how many lines to generate and the max character count.
- Click 'Generate' and pick your favorites. A/B test top options.
Best practices
- Keep it concise: 28–60 characters often performs well.
- Lead with value and clarity; avoid vague clickbait.
- Use numbers, brackets, and power words sparingly: [Guide], 7 tips, Free.
- Add personalization tokens when possible: [First Name], [Company].
- Create urgency honestly: Today only, Ends soon, Last chance.
- A/B test 2–3 variants per campaign and track open rates.
- Avoid spam triggers: ALL CAPS, $$$, too many emojis.
- Preview on mobile; front‑load the most important words.
Examples
- New this week: 7 quick wins for higher open rates
- Your free guide is inside — claim it today
- [First Name], last chance to lock in 20% off
- We saved you a seat for tomorrow’s webinar
FAQs
What is a good subject line length?
Many brands see strong performance between 28–60 characters. Test different lengths for your audience.
Can I avoid spam filters?
Yes. Use natural language, limit punctuation and emojis, avoid ALL CAPS and spammy terms, and keep your sender reputation healthy.
How many ideas should I test?
Start with 2–3 per campaign. Keep the winner and iterate on it in future sends.
Does tone matter?
Absolutely. Match tone to audience and goal: professional for B2B, friendly for newsletters, urgent for limited offers.
How to write an email subject line correctly
Your subject line is the front door to your email. It determines whether people open, skim, or ignore. Master it, and you lift open rate, deliverability, and revenue in one stroke.
Principles that win opens
- Clarity before cleverness: readers should know exactly what they get.
- Lead with benefit: highlight outcome, not features.
- Keep it short: aim for 40–50 characters or 6–9 words.
- Be specific: numbers, names, dates, and concrete nouns beat vague claims.
- Relevance and personalization: segment by intent; use first name, company, or use case only when it adds value.
- Credibility and compliance: no clickbait, no all caps, minimal punctuation, and avoid classic spam triggers.
- Mobile-first: the first 30–40 characters do the heavy lifting.
- Brand consistency: the subject line, sender name, and preheader should tell one coherent story.
Proven formulas with examples
- Benefit + time: 'Cut invoice time by 50% this week'
- Number + promise: '3 ways to boost open rates today'
- Curiosity with restraint: 'The tiny fix that doubled signups'
- Problem → solution: 'Struggling with churn? Try this'
- Question hook: 'Still paying for features you don’t use?'
- Command CTA: 'Book your 10‑minute demo'
- Brackets/clarifiers: '[Webinar] AI for busy marketers'
- Personalization token: 'Alex, your July report is ready'
- Urgency with integrity: 'Last chance: 20% off ends tonight'
Words to prefer vs avoid
- Prefer: specific verbs (get, save, learn, fix), numbers, time markers (today, this week), and clarifiers (free guide, case study).
- Use emojis sparingly and only when on-brand; test for different inboxes.
- Avoid: all caps, multiple exclamation marks, deceptive prefixes like 'RE:' or 'FW:' when not true, and spammy bait like 'FREE!!!' or 'Act now!!!'
Optimization workflow
- Draft 5–10 variants for each send; change angle, length, and verb.
- Pair a compelling preheader that completes the thought of the subject line.
- A/B test on a statistically valid slice; promote the winner to the remainder.
- Segment by lifecycle stage and intent; one size fits none.
- Refresh after fatigue; repeat winners with new framing, not copy‑paste.
- Analyze beyond opens: correlate with CTR, unsubscribes, and spam complaints.
- Respect deliverability: authenticated domain, clean lists, and steady sending cadence.
- Send‑time matters; test windows for your audience, then standardize.
Checklist before sending
- Does the first phrase communicate the core benefit?
- Under 50 characters or still legible on mobile?
- No spam triggers, all caps, or punctuation spam?
- Aligned with sender name and preheader?
- Segmented and personalized only where it helps?
- One clear idea, one promise, one action?
Quick templates you can adapt
- 'Your weekly recap: 3 insights you can use today'
- '[Guide] How to write email subject lines that get opened'
- 'We analyzed 1,000 campaigns so you don’t have to'
- 'You’re missing this from your onboarding flow'
- 'Reminder: registration closes in 6 hours'
- 'Welcome aboard — here’s your first win'
The best subject lines earn attention with clarity, relevance, and trust. Iterate relentlessly, test rigorously, and let your audience’s behavior guide the next draft.