Email Subject Line Grader & Spam Check
Your email subject line is the first thing recipients see — and often the deciding factor between an open and a delete. Our free Email Subject Line Tester analyzes your subject lines in seconds, giving you actionable insights to boost your open rates.
Simply enter your subject line below and get instant feedback.
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💡 Tip: Keep it under 50 characters for best mobile display
Why Your Email Subject Line Matters
The average professional receives over 120 emails per day. With inboxes this crowded, your subject line has just 2-3 seconds to make an impression.
Here’s what the data shows:
- 47% of recipients decide to open an email based solely on the subject line
- 69% of recipients report emails as spam based on the subject line alone
- Emails with personalized subject lines have 26% higher open rates
- Subject lines with 6-10 words have the highest open rates
A weak subject line doesn’t just mean fewer opens — it can damage your sender reputation and land your future emails in spam folders.
What Our Subject Line Tester Analyzes
Our tool evaluates your subject line across five key dimensions:
- Length & Mobile Preview
Most mobile email clients display only 35-40 characters. Desktop clients show around 60. We check if your subject line fits these limits and show you exactly how it will appear on different devices. - Spam Risk Assessment
Certain words and phrases trigger spam filters. Words like “FREE,” “Act Now,” or “Limited Time” can send your email straight to junk. Our database includes 500+ known spam triggers, weighted by severity. - Power Words & Emotional Impact
High-performing subject lines use power words that create urgency, curiosity, or exclusivity. We identify which emotional triggers you’re using — and which you might be missing. - Personalization Signals
Subject lines with “you” or “your” feel more personal and relevant. Questions increase curiosity. Numbers add specificity. We check for all these engagement boosters. - Readability
Complex words and jargon reduce comprehension. We analyze word length and sentence structure to ensure your message is instantly clear.