Email Subject Line Tester

Your subject line decides whether your email gets opened or ignored. Paste one in and this free tool scores it on length, spam triggers, clarity and curiosity — with specific tips to improve it. No signup.

What makes a subject line work

Aim for roughly 30–50 characters (it must read well on mobile), make a specific promise, spark curiosity, and avoid spammy hype. Personalization and a clear benefit help; ALL CAPS, excessive punctuation, and "FREE!!! BUY NOW" hurt both opens and deliverability.

Want proven subject lines and full sequences to plug in? Grab the Creator's Email Swipe Pack, and learn the strategy in how to write a welcome email sequence and email marketing for beginners.