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Your email’s fate is often decided in just a few words—your subject line

We fed Zenie AI hundreds of thousands of email subject lines with above 60% open rates to get you the ultimate, free subject line tester!

Type your best subject lines and analyze their health scores here
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Your subject line scored a

75

Out of 100

Detailed Analysis

Subject Line Success Factors

Your subject line checklist for getting emails opened, read, and clicked. Each factor directly impacts your open rates and engagement.

Length

3/10

4–6 words are recommended for optimal display on mobile devices.
Exp.: "Last Chance: Save 20% on Your Annual Subscription"
...

Personalization

3/10

Incorporate tokens (e.g., {first_name}) to create a tailored message.
Exp.: "{first_name}, Your Custom Report is Ready"
...

Spam Triggers

3/10

Avoid words that commonly trigger spam filters
Exp.: free, guaranteed, act now, money-back, no cost,  urgent
...

FOMO Elements

3/10

Incorporate phrases that evoke urgency and exclusivity
Exp.: Last chance, final call, ending soon, don’t miss out
...

Capital Letters

3/10

Avoid full capitalization or overuse in key words
Exp.: AMAZING DEAL INSIDE! DON'T MISS OUT!
...

Exclamation Marks

3/10

Limit exclamation marks to one (or none) to avoid spammy appearance.
Exp.: Hey folks!, Don’t miss out this offer!!
...

Emoji Use

3/10

Use emojis sparingly and only when they support the message
Exp.: 📊 Your Monthly Analytics Report
...

Word Count

3/10

Aim for 4–9 words to ensure clarity and impact
Exp.: Join Our Exclusive Webinar on Digital Marketing
...

Readability & Sentiment

3/10

Use NLP to assess clarity and tone.
Exp.: Need to update
...

Negative Words

3/10

Avoid language that creates a negative impression
Exp.: Problem, fail, failure, disappoint, disappointment, bad, waste
...

But there’s more!   Zenie AI has analyzed 
what gets opened in millions of inboxes to get you below subject lines for inspiration

Cyber Monday
Black Friday
Christmas
Valentine's Day
Mother's Day
Father's Day
Abandoned cart
Welcome
Sale
New collection
Limited-time offer
Thanksgiving
Diwali
New year
Independence
Don't miss out our BOGO sale!
92%
copied
Black Sale. New arrivals 30% off!
92%
copied
💥 25% Black Friday Code: FRIDAY
92%
copied
Black Friday is back!🔥 Shop now!
92%
copied
🚨 BLACK SALE! Bestsellers 45% off!
92%
copied

If you liked those subject lines & the subject line tester, you might also like a few other tricks from Zenie AI.

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 Create inbox-stopping headlines in seconds with our AI that's trained on thousands of high-performing emails with 60%+ open rates

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Zenie AI suggests the best versions of content by learning from hundreds of thousands of high-converting emails

Frequently Asked Questions

How does the free subject line analyzer work?

Our AI subject line tester analyzes your email subject lines against several key factors that affect your open rates, including length, personalization, spam triggers, and FOMO elements. Simply enter your subject line and receive an instant health score based on data from hundreds of thousands of high-performing emails with open rates of 60% or higher.

What makes this AI subject line generator different from other tools?

Zenie AI has been trained on email subject lines that achieved open rates above 60% across millions of inboxes. Unlike generic tools, our subject line tester provides actionable insights on spam triggers, optimal word count, emoji usage, and personalization opportunities to maximize your email performance.

Is the subject line tester really free to use?

Yes, our AI subject line analyzer is completely free with no credit card required. You can test unlimited subject lines and access all scoring features. For advanced email marketing automation and campaign building, you can try our full platform free for 14 days.

Can the subject line analyzer help avoid spam filters?

Yes. Our free subject line tester specifically checks for common spam trigger words, such as "free," "guaranteed," "act now," and "urgent." It also analyzes capitalization patterns, excessive punctuation, and other factors that commonly cause emails to be directed to spam folders.

What subject line length does the AI recommend for best open rates?

Our subject line analyzer recommends 4-6 words for optimal mobile display, with a total range of 4-9 words for maximum impact. The tool automatically flags subject lines that are too long or too short and provides suggestions for improvement based on successful email campaigns.

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