Free Email Subject
Line Tester
Score in real time. Spot spam triggers. Preview in 4 email clients. A/B test. Get AI rewrites.
How Subject Line Scoring Works
7 factors that directly influence whether your email gets opened or ignored.
Ideal Length (20 pts)
40–60 characters is the sweet spot. Shorter loses context; longer clips on Gmail Mobile.
Spam Triggers (25 pts)
Words like 'guaranteed', 'act now' and 'click here' trigger spam filters and kill deliverability.
Power Words (15 pts)
Urgency, curiosity, FOMO and value words drive opens — each triggers a different emotional response.
Capitalisation (10 pts)
ALL CAPS screams spam. Sentence case or title case builds far more trust with both readers and filters.
Punctuation (10 pts)
One exclamation mark is fine. Two starts to look desperate. Three or more hurts open rates significantly.
Emoji (10 pts)
Zero or one emoji maximises impact. Multiple emojis reduce trust and can trigger mobile spam filters.
Frequently Asked Questions
What is a good email subject line score?
A score of 80+ (grade A) is excellent and should deliver strong open rates. 65–79 (grade B) is good. Aim for at least 65 to maximise performance. Anything under 50 needs significant improvement before sending.
What are email spam trigger words?
Spam triggers are phrases that spam filters and email clients flag as suspicious, including 'guaranteed', 'act now', 'click here' and 'earn money'. Removing all spam triggers is the single highest-impact change you can make to improve deliverability.
What is the ideal email subject line length?
The ideal email subject line is 40–60 characters. This ensures full display in Gmail desktop (up to 70 chars) and Gmail mobile (up to 40 chars) without clipping. Subjects under 20 characters lack context; over 80 and most clients will truncate them.
How do I use A/B compare mode?
Click the 'A/B Compare' button above the input. Two subject line fields appear side by side. Enter your two versions and get instant scores for both. The winner is highlighted with a green badge — use it to pick the stronger subject line before you send.
What are email power words and how do they work?
Power words are emotionally charged words that drive action. Urgency words (now, tonight, expires, deadline) create time pressure. Curiosity words (secret, revealed, truth) make readers want to know more. FOMO words (exclusive, rare, limited edition) create fear of missing out. Value words (save, deal, proven, results) communicate clear benefit.
How do I improve my email open rate?
Keep your subject line between 40–60 characters, include 1–2 power words from the urgency or curiosity categories, remove all spam trigger words, add a specific number for credibility, limit punctuation to one mark, and use a maximum of one emoji. Use the AI alternatives feature to get 5 professionally rewritten options.
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