Email Marketing

17 Subject Line Tester Tools Your Marketing Team Can Use

Do your subject lines draw readers in and drive them to open your emails?

If not, you need to make use of an email subject line tester before hitting send.

But what's an email subject line tester?

It's a tool that analyzes email subject lines and tells you what you need to do to improve them. It checks for factors such as length, emotion, grammar, punctuation, personalization, etc.

Why should you care about subject lines?

Consider how many emails your recipients receive in a day from different sources. Then, factor in research reporting that the total number of emails sent and received will exceed 333 billion in 2022.

Image via Radicati

This begs the question:

Why should the recipient choose to open your email over others?

It's for this reason you need a subject line tester.

You need a tool that can increase your chances of getting higher open and click-through rates for your emails. A tool that recommends what words you need to change or include to improve deliverability and readability.

But which are the best subject line tester tools?

Find out below.

Disclaimer: This content contains some affiliate links for which we will earn a commission (at no additional cost to you). This is to ensure that we can keep creating free content for you.

Top 17 Subject Line Tester Tools for Higher Open Rates

Subject lines are the first thing your recipient sees in their email inbox.

These are often the deciding factor on whether the recipient opens your email or not. Therefore, it's crucial to stop relying on intuition and leverage tools that offer cold hard data on creating subject lines that work.

And in this section, we list out the best subject line tester tools your business can use to improve your email open rates.

Check these out.

1. The Email Subject Line Analyzer by Attrock

Image via Attrock

We kickstart with our very own Email Subject Line Analyzer.

We are a digital marketing company, and since email marketing is part of the services we offer when helping brands drive great returns, we created a tool to make it possible.

But what makes our email subject line tester stand out?

The Email Subject Line Analyzer by Attrock assesses and scores your subject lines based on whether they can drive more clicks. This way, it becomes easy for you to write compelling and emotional subject lines that get more clicks and opens.

Additionally, you get suggestions on how to improve your subject line, including the ideal number of words, personalization, character count, etc. You can also access a word bank with words you can consider adding to your subject line.

But that's not all.

You also get a preview of how your email will look in your recipient's inbox and what it lacks.

Key Features

  • Feedback on the expected subject line performance
  • Suggestions on improving the subject line to get higher open rates
  • Preview of the subject line on different devices
  • Word bank with suggestions on phrases you can add to your subject line
  • Recommendations on best practices for personalizing a subject line

Pros

  • More detailed analysis than most other tools

Cons

  • Does not provide industry-specific analysis

Usability

  • Easy to use

Tool Level

  • Beginner/Intermediate/Expert

Pricing

  • Free

2. TestSubject

Image via Zurb

This subject line tester ensures that your subject lines display properly in the recipients inboxes without cutting off words.

Since most people open emails based on subject lines, you need to ensure you write subject lines that increase click-through and open rates so that you can increase conversions.

Key Features

  • Tests how subject lines will appear on various devices
  • Reviews text on the preheader
  • Shows how your sender name appears on mobile devices

Pro

  • Extremely good for seeing previews of subject lines of various devices

Cons

  • Does not show suggestions for improving email subject lines to increase open rates

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

3. SubjectLine.com

Image via SubjectLine.com

This subject line tester gives you an overall score of your subject line with reasons that made you lose points.

It's one of the email marketing tools you can leverage to better understand what kind of email content can improve open and response rates.

Key Features

  • Offers results based on factors like urgency, length, prepositions, spam-related issues, etc.
  • Advises whether email subject lines need to be rewritten

Pros

  • It evaluates filtering and deliverability issues so that your emails don’t trigger spam filters

Cons

  • It does not specify ways to improve email open rates by optimizing subject lines

Usability

  • Easy to use

Tool Level

  • Beginner/Intermediate

Pricing

  • Free

4. The #1 Email Subject Line Tester by CoSchedule

Image via CoSchedule

Improve your email and newsletter open rates by leveraging this subject line tester from CoSchedule.

Why use it?

You get suggestions on how to optimize the subject line for higher open rates.

Key Features

  • A word bank with words that increase and decrease opens
  • Gives results depending on case used, number of words used, emojis, character count, etc.

Pros

  • Offers a preview of your email subject lines on desktop and mobile

Cons

  • It offers limited factors showing what you can do to increase open rates

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

5. SendCheckIt

Image via SendCheckIt

This subject line tester claims to compare your subject line against more than 100K other emails sent by marketers.

And considering how content personalization is crucial, this subject line tester also scores your performance based on this factor.

Key Features

  • It gives you an overall score out of 100
  • Considers factors including scanability, length, sentiment, personalization, and reading level
  • Informs you of factors that could affect deliverability like an exclamation mark, spammy words, etc.

Pros

  • In-depth score breakdown
  • API access

Cons

  • Some of the suggestions require further explanation

Usability

  • Moderately easy to use

Tool Level

  • Intermediate/Expert

Pricing

  • Free

6. Email Subject Line Grader

Image via Email Subject Line Grader

This subject line tester by Net Atlantic helps you score your headline and calculate character count.

It’s also a good tool when you want to calculate word balance and mix.

Key Features

  • Get results on the type of subject line used
  • Shows word and character count

Pros

  • Results account for whether you’ve used the right mix of words and whether they balance out

Cons

  • It does not show a preview of email subject lines on different devices
  • The analysis is not as detailed as many other tools

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

7. Mizy's Free Email Subject Line Tester by Automizy

Image via Automizy

Unlike other subject line testers that score against best practices, Mizy leverages deep learning to analyze email campaigns and make predictions.

It's an artificial intelligence-powered platform that grades subject lines using data from over 1 million campaigns.

Key Features

  • Offers templates to improve your email subject lines
  • It's possible to upload campaign data for better recommendations and personalized scoring
  • Leverages AI to grade subject lines by comparing them to over a million other campaigns

Pros

  • Use the power of AI, which is something that most other tools don’t offer

Cons

  • There is no description of what factors you should change for better performance, and you have to rely on the templates alone

Usability

  • Moderately easy to use

Tool Level

  • Intermediate/Expert

Pricing

  • Free

8. Refine by Moosend

Image via Moosend

With the Refine subject line tester, you leverage artificial intelligence to test subject lines and create those that resonate with your audience.

And if you want to improve your email lead generation and conversion rate, you need to leverage a subject line tester like this one to get higher open rates.

Key Features

  • Scores subject lines depending on your industry
  • Estimates open rate potential and whether you meet the average industry standards
  • Offers recommendations to improve the subject lines

Pros

  • Leverages AI to assess subject lines, instead of common best practices

Cons

  • It does not offer a preview of the subject line on various devices

Usability

  • Easy to use

Tool Level

  • Beginner/Intermediate

Pricing

  • Free

9. Headline Analyzer by AMI

Image via Advanced Marketing Institute

If you want to find the emotional marketing value of your subject lines, you can use this ehadline analyzer by AMI. It is technically not an email subject line tester, but can act as one for this specific purpose.If you want to find the emotional marketing value of your subject lines, you can use this ehadline analyzer by AMI. It is technically not an email subject line tester, but can act as one for this specific purpose..

And since successful copywriting requires you to write content that touches your clients emotionally, you need a subject line tester that factors in this variable.

Key Features

  • Scores the emotional marketing values of headlines in relation to the total number of words used
  • Helps you discover what emotion your headline mostly stirs – intellectual, empathetic, spiritual, etc.

Pros

  • Goes beyond common metrics and also tests the sentimental value of subject lines

Cons

  • It does not offer a comprehensive comparison of factors, and the results may not be clear on what needs to change to improve your headlines

Usability

  • Moderately easy to use

Tool Level

  • Intermediate/Expert

Pricing

  • Free

10. Email Subject Line Tester by Capitalize My Title

Image via Capitalize My Title

This subject line tester uses over 60 different data points to score your subject lines.

Want to know the best part?

You can use it to capitalize your subject lines once you finish correcting them for readability and deliverability.

Key Features

  • Enables you to test subject lines and score them on a scale of 1-100
  • Offers recommendations on what areas you need to improve

Pros

  • An in-depth explanation on what to improve
  • Option to capitalize subject lines

Cons

  • It does not offer a preview of the subject line on various devices

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

11. FREE Email Subject Line Tester by MailNinja

Image via MailNinja

MailNinja's subject line tester is another tool that offers in-depth analysis on what you need to change for your subject line to drive positive results.

Incorporating these recommendations may be the key to boosting your email open rates and staying ahead of the competition.

Key Features

  • It checks for factors like character and word count, spammy words, action words, etc.
  • Offers recommendations on what to change

Pros

  • Deep analysis of factors

Cons

  • Unlike other subject line tester tools, you receive results only after providing contact information

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

12. Email Subject Line Analyzer Tool

Image Via IsItWP

With the IsItWP email subject line tester, you can ensure that your subject lines have the perfect word balance, are scannable, and get straight to the point.

Additionally, it can help you leverage power words that improve your open rates.

Key Features

  • Gives recommendations on what to change
  • Scores performance based on factors such as characters, number of words, emoji count, etc.
  • Offers a preview of your email in the inbox

Pros

  • Provides detailed explanations of why a suggested change is important and how it can help improve open rates

Cons

  • The preview is only available for desktop and not mobile devices

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

13. Subject Line Helper by Mailchimp

Image via Mailchimp

If you are looking for a subject line tester that offers comprehensive features to ace your email marketing campaign, Mailchimp is a great choice. Its Subject Line Helper is a tool that comes free with your Mailchimp account.

In addition to offering a subject line tester tool, Mailchimp is used to build ad campaigns, create beautiful landing pages, and send branded emails.

Let’s see what else makes Mailchimp an effective subject line tester.

Key Features

  • Data-driven, real-time inputs on character count, word count, emojis, and punctuation
  • A/B test and compare subject lines to choose the best one. Mailchimp automatically sends the best email.
  • The subject line helper compares your email subject line with the performance of millions of emails to see if it follows best practices.

Pros

  • Real-time, data-driven inputs on improving emojis, punctuation, word, and character count
  • A/B testing of subject lines

Cons

  • Unlike many other subject line tester tools listed here, Mailchimp does not evaluate sentiment, scanability, and reading level.

Usability

  • This subject line tester is easy to use

Tool Level

  • Beginner

Pricing

  • Free

14. Spam Check by Postmark

Image via Postmark

Are a large amount of the emails you send being marked as spam?

You should consider using a subject line tester tool such as Postmark’s Spam Check. This tool not only acts as a subject line tester but helps make sure that none of your emails are being misfiled as spam.

Read on to know what other features make the Spam Check a viable subject line tester tool.

Key Features

  • Checks the subject line and the entire email to evaluate the likelihood of it being marked as spam by servers.
  • Spam Score helps understand the elements that are not working in your email.
  • Suggestions to improve your email copy and headline.
  • Granular insights on clicks, opens, bounces, and delivery.

Pros

  • Granular insights on clicks, opens, bounces, and delivery.

Cons

  • Does not analyze the sentiment, personalization, or readability of an email subject line.

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

15. Subject Line Tester by Omnisend

Image via Omnisend

Omnisend is a must-have subject line tester tool for teams who are serious about how they write emails. In addition to subject line testing, the tool also helps you with segment testing, email reporting, and email marketing automation.

You can A/B test your email subject lines to zero in on the best one.

That’s not all. The subject line tester evaluates, words, characters, and the length of the subject line and gives you suggestions on replacing spam-triggering words with safer words.

Check out this subject line tester’s features, pros, and cons.

Key Features

  • Data-backed percentage score of email subject line
  • Analyzes scannability, character and word count, capitalization, length, negative and helpful words
  • Alerts on spammy words, and excessive punctuation
  • Desktop and mobile previews

Pros

  • Comprehensive subject line tester tool.

Cons

  • Does not offer personalization suggestions.

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free

16. Lavender

Image via Lavender

Lavender is the subject line tester you need to write impactful emails that have high open and response rates.

It offers AI-powered features that help you create persuasive emails, and ace your email marketing campaigns.

Let’s take a closer look at this subject line tester’s features, pros, and cons.

Key Features

  • AI-powered email intelligence
  • Rich insights into your recipients including their personality type, calendar events, and social data
  • Analyzes and scores email and subject line
  • Word and sentence suggestions

Pros

  • Actionable intelligence into recipients that helps tailor email subject line and copy.

Cons

  • Integration with Outreach needs improvement.

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Free: Up to 5 email analyses per month
  • Individual Pro: $29 per month
  • Teams: $49 per user per month

17. Email Copy Analyzer by Mailshake

Image via Mailshake

Mailshake is a great tool for any marketer who needs to run an email campaign. It's an easy-to-use subject line tester that will help you send out emails that deliver the results you seek.

Mailshake offers a variety of features such as A/B testing, automation, and drip campaigns. You can also use Mailshake for social media marketing and website traffic optimization.

Check out the features of this subject line tester.

Key Features

  • Evaluates email copy and subject line for length and spam triggering words
  • Recommendations to improve copy and subject line to optimize readability and deliverability
  • Assistance on writing personalized subject lines to achieve high open rates

Pros

  • An intuitive tool that is easy to use for beginners.

Cons

  • Does not integrate with G-Suite or Gmail.

Usability

  • Easy to use

Tool Level

  • Beginner

Pricing

  • Email Outreach: $44 per user per month

FAQs

Q1. How do you test a subject line?

A. Use a subject line tester like the one offered by Attrock to test various aspects, including:

  • Personalization
  • Length
  • Word usage
  • Subject line type
  • Case used
  • Previews of the subject line on different devices
  • And more!

Q2. Why is subject line testing important?

A. Testing your subject lines before sending the emails helps you optimize them and ensure that they get the desired open rates. Subject line testing can help you avoid common mistakes and create engaging and high-coverting subject lines that compel recipients to click on your email.

Q3. What is Subject line A/B testing?

A. It's a process of comparing how one version of your email subject line performs when sent to an audience compared to another.

For example, you can send one version of your subject line to a percentage of your recipients and send another version to the rest. Then, after comparison, the subject line that receives the most opens emerges as a winner.

You can then use this winning subject line when sending emails to the rest of your contacts.

Q4. What is the most reliable way to test whether your subject line will get more people to open their email?

A. The simple answer is to use a subject line tester to optimize your subject lines before sending your emails. These tools analyze your subject lines on multiple parameters and give suggestions on how to improve them.

Q5. What is subject line optimization?

A. It is the process of analyzing your subject lines using a testing tool and then incorporating the suggestions provided to make them more engaging.

Q6. What are ssubject lines?

A. Subject lines are a sort of introduction to an email and are visible in a recipient’s inbox even if they do not open an email. Email subject lines provide information about the email and help people decide whether they want to open the email.

Q7. Are subject line testing sites valid?

A. Yes, they are.

They make the process of testing subject lines easier and provide a detailed analysis of subject lines and ways to improve them.

Q8. Which is the best email subject line tester?

A. Use this list to find some of the best email subject line testers:

  • The Email Subject Analyzer by Attrock
  • TestSubject by Zurb
  • com
  • The #1 Email Subject Line Tester by CoSchedule
  • SendCheckIt
  • Email Subject Line Grader
  • Mizy’s Free Email Subject Line Tester by Automizy
  • Refine by Moosend
  • Headline Analyser by AMI
  • Email Subject Line Tester by Capitalize My Title
  • Email Subject Line Analyzer Tool
  • Subject Line Helper by Mailchimp
  • Spam Check by Postmark
  • Subject Line Tester by Omnisend
  • Lavender
  • Email Copy Analyzer by Mailshake

Choose the Best Email Subject Line Tester for Your Needs

With the right subject line tester, you can improve deliverability and open rates of your emails.

So, keep testing your subject lines, analyze different metrics, and see what works best for your recipients.

Which of the subject line tester tools do you like?

Share your experience with the subject line tester and how it helped you improve your email marketing results in the comments.

Disclaimer: This content contains some affiliate links for which we will earn a commission (at no additional cost to you). This is to ensure that we can keep creating free content for you.

Gaurav Sharma

Gaurav Sharma is the Founder and CEO of Attrock, a results-driven digital marketing company. Grew an agency from 5-figure to 7-figure revenue in just two years | 10X leads | 2.8X conversions | 300K organic monthly traffic | 5K keywords on page 1. He also contributes to top publications like HuffPost, Adweek, Business2Community, TechCrunch, and more.

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