Subject Line Tester

Email Subject Line Tester

Boost your email open rates: analyze and improve your subject lines with our free tester before sending out your next campaign.

Looking for someone to test subject lines? We have your back. It takes skill to write the ideal email subject line. To achieve the highest open rates, you must strike the perfect balance between inventiveness and the appropriate level of audience understanding. And even though it could seem like a difficult task, fortunately, there are topic line tests. These resources facilitate the procedure.


This blog post will go over 11 subject line testers, both free and paid, that you may utilize to get better results. We’ll cover everything, from tools that gauge how words affect readers emotionally to those that may help you determine the ideal subject line length for mobile devices and prevent your emails from being flagged as spam.


Although some creativity is still required when coming up with subject lines, technology has made it easy to use data. You’ll discover a variety of tools in the list below, each with unique features and functionalities. Some tools are more advanced than others, but even those with fewer features offer a distinctive viewpoint that can aid in producing results.

Email Subject Line Tester

Subject Line Testers – 11 Tools to Increase Open Rates

1. Test Subject by Zurb

Most people are unaware of this, yet mobile devices frequently shorten email subject lines. What happened? subject lines that are difficult to read because they are so long. When Zurb realized this, he decided to act. Test Subject was created by their product design team to guarantee that mobile email subject lines receive the attention they require to produce outcomes.


And that was a wise decision. More than 57% of all internet traffic in the US is generated by smartphones, and by 2023, analysts predict that there will be 347 billion emails sent and received worldwide. Email subject line optimization for mobile will result in smarter, more enticing, and more successful email marketing.


2. Send Check It 

Check to Send One of the most thorough topic line testers is this one. It provides a list of the 16 factors that subject lines are judged against in addition to an overall score and advice on how to improve your subject line. The list of requirements is also quite useful. It examines the presence of emojis, punctuation, and spam elements.


Here is a list of each of the 16 requirements in full:


3. Mizy by Automizy

According to Mizy, it approaches topic lines in a unique way. Mizy employs AI and deep learning, in contrast to other subject line testers, to assist you in finding the ideal email subject line. Additionally, Mizy has access to an email database and is aware of the open and click-through rates of each email.


Mizy’s deep learning neural network makes this possible. It has the capacity to gather information and reorganize itself in order to deliver more beneficial insights on what is and isn’t producing the best email results. After you submit your subject line, Mizy will produce an overall performance score (out of 100) and offer suggestions for how to make your copy stronger.


4. Email Subject Line Grader by Net Atlantic

Email Subject Line Grader provides a performance score that relies on 4 different criteria. These are – 

An explanation of the several kinds of subject lines you can use. (consider subject lines with “how-to” or “question”). Additionally, users are given advice on how to make their subject lines stronger.

The number of characters used. According to research, email subject lines with 60 characters or fewer are the most effective. The tool will inform you of the length of your subject line and provide suggestions based on that length.

How many words were used? Get opinions on how many words should be used to engage readers. 

An indicator of how many actions, passion, and power words were employed. The tool will suggest adding a handful of these to enhance your copy if your subject line is missing any of these.


5. Spam Check by Postmark

Spam detectors are harsh. They can obliterate email marketing campaigns, making it more difficult to produce fruitful outcomes. However, Postmark allows you to bypass spam filters. You can enter the entire text of your email—including the subject line—into Spam Check’s tool. After that, it evaluates the text and assigns a spam rating.



One of the more thorough topic line screening tests is available at The tool, according to the provider, tests and evaluates filtering and deliverability difficulties using more than 800 different rules. In other words, your results should serve as a reliable predictor of how well your copy will work. Results provide a score and a breakdown of where your subject line is underperforming. You also get suggestions for how to make your copy stronger in the form of a brief blurb.


7. Touchstone

A virtual subject line testing platform is called Touchstone. With a database of more than 21 billion emails, you may test subject lines. Results are displayed as a percentage, showing how well your subject line would do in comparison to subject lines for emails in your industry that were comparable. In order to locate the best version as quickly as possible, you can test up to 10 subject lines at once.


8. ISnotSPAM

Concerned that spam filters will mark our emails? Attempt ISnotSPAM. It can be used for subject lines even though it’s normally used to test an email’s body copy. It runs five tests, including the following:

Visit the tool’s page and copy the offered special email address to begin going. Use the email address and paste your subject line there in the email body to send it (leave). Click “View Your Report” to see the results after that.


9. Subject Line Tester from Moosend

Similar to Mizy, Moosend’s subject line tester employs AI for in-the-moment analysis. You may get a fair idea of how well your subject line will perform by comparing your results to those in your field. Additionally, the tool offers advice on how to increase your open rate.


10. Emotional Marketing Value Headline Analyzer

A number called “Emotional Marketing Value” assesses the emotional impact of a group of words. Although it may be difficult to imagine, that is based on a government study conducted by Dr. Hakim Chishti in the 1960s and 1970s. Despite the fact that this tool was made for headlines, it may also be used for email subject lines, which essentially email headlines. Both are intended to accomplish the same goal—inspire your reader to read more. Your article will receive a final grade from the Emotional Marketing Value Headline Analyser. It also shows the audience to which your copy is most appealing.


11. Email Subject Line Tester

Although CoSchedule is more renowned for its content marketing software, one of the most useful tools out there right now is probably its email subject line tester. It’s intended to assist marketers in writing subject lines that are more empathetic and increase conversion.


It achieves this by assigning grades to your copy based on eight factors:


  1. Case – Get feedback on which case works best for subject lines.
  2. Overall score out of 100 – The higher your score the more effective your subject line.
  3. Numbers- Whether you’ve included any numbers. 
  4. Use of words that increase opens –These are positive words or words from CoSchedule’s
  5. Character count –The number of characters used
  6. Appearance preview – Get a preview of how your subject line will look on desktop and mobile.
  7. Emoji count – How many emojis are used?

Word count – The number of words used.