Free Email Subject Line Tester
Score your email subject line before you send. Get feedback on length, spam risk, and engagement potential.
How it works
Type your subject line
Enter the subject line you plan to use in your campaign.
We score it across 12+ factors
Length, word count, spam triggers, capitalization, personalization, urgency, and more.
Get a score with improvement tips
See what is working, what is not, and specific suggestions to improve open rates.
Why this matters
Your subject line determines whether your email gets opened or ignored. 47% of recipients decide to open an email based on the subject line alone. In cold outreach, a bad subject line means your carefully written email never gets read.
Test subject lines in real campaigns
SendKit A/B tests your subject lines across live campaigns and shows you which ones drive the most opens.
A/B testing
Test multiple subject lines against each other in real campaigns
Open rate tracking
See which subject lines perform best across your campaigns
AI suggestions
Get AI-generated subject line alternatives based on your email content
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Got questions? We've got answers.
Good subject lines are 6-10 words, avoid spam triggers, create curiosity or urgency, and feel personal. They should be specific enough to set expectations but intriguing enough to earn the open.
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