Email Subject Line Tester
Analyze your email subject lines to improve open rates. Get instant feedback, AI-powered suggestions, and mobile previews.
Master the First Impression
Your subject line decides whether your email gets opened or ignored. Our free tester uses data-backed rules and AI to help you write headlines that demand attention.
Why Test Your Subject Line?
Boost Open Rates
35% of recipients open emails based on the subject line alone. A higher score here means more eyes on your content.
Avoid the Spam Folder
We check for “spam trigger words” (like Free, Guarantee, Urgent) that can hurt your deliverability.
Mobile Optimization
Over 50% of emails are read on mobile. Our tool shows you exactly where your text will get cut off on smaller screens.
3 Ways to Write Better Subject Lines
Keep it Short
Aim for 40-60 characters. Long subject lines get truncated, hiding your most important message.
Use Power Words
Words like “Exclusive,” “Update,” and “Introducing” trigger curiosity. Our tool highlights positive keywords for you.
Leverage AI
Stuck? Use the AI Improvements feature in this tool to instantly generate 3 creative alternatives.
Action plan
Your Subject Line is Perfect. Now, Will It Land in the Inbox?
Ensure your prospect will see and open your emails. From technical setup with DMARC and SPF to using email warmup, deliverability is a complex topic. No worry, we can advise you on where to start.
Audit your current email setup
Get a complete, personalized action plan for your entire emailing system, from technical setup and list building to a full deliverability scorecard.
Take the 5-min AssessmentFrequently Asked Questions
What is an email subject line tester?
A subject line tester is a tool that analyzes your headline to predict its open rate performance. It checks for best practices—like character count, emotional impact, and power words—while scanning for negative “spam trigger” keywords.
How does the AI improvement feature work?
Our tool uses advanced Language Models (LLMs) to understand the context of your email (e.g., Newsletter vs. Cold Outreach). It then generates three alternative subject lines optimized for higher engagement based on your original draft.
Should I use emojis in my subject line?
Yes, but sparingly. Data shows that using 1 emoji can boost open rates by adding visual flair to a crowded inbox. However, using more than 2 often looks like spam and can trigger filters.
Does this tool verify if my email will go to spam?
It checks for “spam trigger words” in your subject line (like “Free,” “Cash,” or “Urgent”). However, it does not check your technical domain reputation. For that, use our Email Health Checker.
Do you save my subject line data?
No. We respect your privacy. The subject line you input is processed instantly to generate the score and suggestions, and is not stored or used for any other purpose.
What is A/B testing for subject lines?
A/B testing involves sending two different subject lines to a small portion of your audience (e.g., 10%) to see which one gets more opens. You then send the winning version to the remaining 90% of your list.