Subject lines that get opened, not just sent.
Your subject line determines whether anything else you wrote matters. This library contains 100+ subject lines organized by approach, tested across real B2B campaigns.
Why subject lines matter more than you think
The average professional gets 120 emails per day. Your cold email competes with every one of them. The subject line is your one shot at getting noticed. Too clever and it feels like spam. Too vague and it gets skipped. Too long and it gets truncated on mobile. The best cold email subject lines are short, specific, and create enough curiosity to earn the open without being clickbait. This library gives you proven frameworks and real examples.
What's in this library
- Question-based subject lines that invite engagement
- Direct subject lines that state the value upfront
- Curiosity-driven subject lines that earn the open
- Personalized subject lines using name, company, or signal
- Referral and mutual connection subject lines
- Re-engagement subject lines for follow-ups
- Subject line formulas you can customize for any ICP
- Anti-patterns: subject lines that consistently underperform
Where to go from here
Great subject lines get opens. Great body copy gets replies. Check our Cold Email Templates for full email sequences that pair with these subject lines. For deliverability (because opens don't matter if you're in spam), see our Deliverability Guide. Or let us write all your cold email copy -- subject lines included.
Frequently asked questions
What open rate should a good subject line get?
For cold email to B2B contacts, 50-70% open rates are strong (after adjusting for Apple MPP inflation). Below 40% usually indicates a subject line or deliverability problem.
Should I personalize subject lines?
It depends. {first_name} in the subject line works but is overused. Referencing their company name or a specific signal tends to outperform basic name personalization.
How long should a subject line be?
Under 50 characters. Mobile truncates at 35-40 characters, and most of your audience reads email on mobile. Short beats clever every time.
Let us write subject lines that convert.
Book a call and we'll A/B test subject lines optimized for your ICP.