100% Free · Runs in your browser

Email Subject Line Tester

Score your subject line on length, spam triggers & tone before you send it to 5,000 people. Unlimited, instant.

Need the body too? Run the full email through the spam test or grab a proven template

★ Trustpilot
Rated 4.8/5 · 200+ reviews
★
★
★
★
★
✓ Verified· May 2, 2026

“Replaced Apollo overnight. Reply rate went from 2% to 14% in week one. Wish I found this sooner.”

Natasha B.
Natasha B.
Founder, B2B SaaS

What makes a cold email subject line work

The best-performing cold subjects share three traits: short (1-5 words), lowercase or sentence case (like a colleague writes), and specific to the reader (their company, their metric, their launch). "quick question about Acme's onboarding" beats "Revolutionize Your Onboarding Today!" every time.

Remember: the subject line only buys the open. Replies come from the body and the list, so verify addresses with the free email verifier and browse the deliverability guide.

Customer reviews

2,400+ users. Real results.

Don't take our word for it

Great subject. Now send 300,000 of them.

Get lifetime access to lead scraping, a 420M+ B2B database, email verification and cold email sending. One payment, no monthly fees.

Claim Lifetime Deal from $9.90
30-day money-back guarantee Instant access 12,400+ teams