10 Free Email Subject Line Testers Your Marketing Team Can Use

The subject line, for all its simplicity, is far from simple. 

It’s not easy to distill an email’s essence, let alone make it stand out. Crafting a killer subject line can be challenging, too. 

The vein popping up on the forehead – we get it! It’s hard. 

Fortunately, you can rely on email subject line testers! Get a fast, objective analysis of your copy and also satisfy the writer’s qualm. 

(You know, the old “perfectionist’s itch,” boxing you in…)

This blog post offers a peek into the best 10 email subject line analyzers. Our team has explored these tools, and they fit the bill.  

Below are the 10 subject line testing tools we’ll be exploring, along with 10 amazing email subject line examples in the end:

• Refine by Moosend
  
• Free Subject Line Tester
  
• Subject Line Tester by Omnisend
  
• SubjectLine.com
  
• TestSubject by Zurb
  
• Email Subject Line Grader
  
• CoSchedule
  
• Headline Analyzer by AMI
  
• Spam Check by Postmark
  
• Email Copy Analyzer
  
• 10 Examples of Well-tested Email Subject Lines

(Note that the list is not arranged according to the merit of each tool, such that the first is the best and the last not so.)

1. Refine by Moosend

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Refine by Moosend uses AI to “refine” your subject lines. The tool scores subject lines based on your industry, tells you their open potential, and offers recommendations to improve the subject line copy. 
Refine by Moosend is easy to use and very effective. 

2. Free Subject Line Tester

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The Free Subject Line Tester by Email Tool Tester not just analyzes subject lines but shows you how they’ll look on various mobile devices. 

Currently, the tool supports iPhone 14, iPhone SE, iPad (10th Gen), Google Pixel 7, and Samsung S22 Ultra. 
The tool is super easy to use and displays the character count of every subject line you test. We say, go for it! 

3. Subject Line Tester by Omnisend

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The Subject Line Tester by Omnisend scores subject lines in percentages and analyzes punctuation, spammy words, and character and word length. The tool offers both mobile and desktop previews.
For us, the high point of Omnisend’s tool is the anti-spam feature. 

4. SubjectLine.com 

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SubjectLine.com offers insights into your subject line, highlighting why it passed or failed. It scores your copy and gives a list of alternative lines. 

Significantly, it analyzes the urgency of the copy because that’s a hallmark of a good subject line. Again, it’s easy and fun to use. 

5. TestSubject by Zurb

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This email subject line analyzer by Zurb tests how your subject line will appear on various devices, reviews preheader text, and also gives a preview of the sender name on the most popular mobile devices. 

It currently supports iPhone 6, iPhone 6 Plus, and Samsung Galaxy Note 5.

6. Email Subject Line Grader

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Email Subject Line Grader by Net Atlantic scores your subject line, gives you the word and character count, and also evaluates word mixture and balance. 
The high point of this tool is the focus on “action words.” The use of action words can make subject lines super-compelling. The tool rates the use of these words in percentage. It’s easy to use and quite revelatory.

7. CoSchedule 

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CoSchedule’s email subject tester is the only one on this list that factors in emojis while analyzing subject lines. 
The tool offers both mobile and desktop previews. 

 

8. Headline Analyzer by AMI

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The Headline Analyzer by Advanced Marketing Institute is technically an email headline tester. But you can use it to test subject line copy. 
The Analyzer’s highlight is that it evaluates the emotional value of your copy. Depending on the words used, it categorizes your copy by different types of emotion. The only turn-off? Enough with those ads already! 

9. Spam Check by Postmark

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Are you absolutely sure that your email copy isn’t spammy?

Sign into Spam Check to evaluate your subject line, preheader text, and email copy, and be sure. It goes beyond just spammy words. Which is in line with how inbox service providers (ISPs) are evolving. 

10. Email Copy Analyzer

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Email Copy Analyzer by Mailshake offers more than subject line testing, in fact you can use it to run email campaigns as well. 

But coming to subject lines, it tests your copy for length, spam, readability, and personalization. As an extension of this, you can A/B-test your subject lines as well to see which variant performs better. 

10 Examples of Well-tested Email Subject Lines

The following are some of our latest favorite email subject lines:

1. This subject line could be better. Here’s how, by MailPoet.
   
2. [insert dad joke], by Turo.
   
3. As SEEN in the Press 👀, by Seen.
   
4. SAY HI TO *GRAZOLA* 🥣, by Graza.
   
5. NEW, NOW, by Alp N Rock. 
   
6. United Sodas upgrade loading… 🟩🟩🟩⬜️, by United Sodas
   
7. CAUGHT YA, by Halfdays. 

8. 🚶 Ah sh*t, here we go again, by Cleo. 

9. Our new product sucks…, by Fellow.
   
10. Have an Ice Day! 🍦, by DesignbyHumans
    

Admittedly, these subject lines are contextual, urgent, emotional, detailed, intriguing, visual, and earned. 

Test for Yourself, Create for People

Kath Pay, email marketing expert and founder of Holistic Email Marketing, points out the “longitudinal gains” of email marketing.

She contends that since email is a push channel, just showing up can be valuable. So, even if someone deletes your email, they couldn’t have missed the subject line. This is not trivial; people may save your email for later or keep the information in mind. This is the nudge effect set in motion.

As Pay cautions, “Don’t underestimate the power of your subject line — it can influence much more than a simple click.”

The email subject line testers we shared can help you sharpen your subject copy to not only generate opens but also trigger conversions.

Speaking of, check out our top 100 holiday subject lines in 2024-25.