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 is projected to reach 392.5 billion in 2026.
Image via Statista
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.
How We Chose the Best Subject Line Testers
- Features: We thoroughly assessed the range of features offered by subject line tester tools to determine their effectiveness in assisting email marketers. We prioritized tools that can cater to different needs by offering comprehensive evaluations, including character count, word usage, sentiment analysis, and more.
- Accuracy: Data accuracy is paramount when it comes to evaluating subject line effectiveness. We favor subject line tester tools that provide accurate insights based on real-time data and avoid ones that provide vague or limited recommendations.
- Price: Our selection process considers a diverse range of tools to cater to various budgets and needs. We include both free and paid subject line tester tools to accommodate marketers at different stages. While price is an important factor, we also assess the value provided in relation to the tool's capabilities.
- Reviews: Feedback from existing users plays a crucial role in our evaluation process. We carefully analyze customer reviews to understand the user experience, usability, and effectiveness of each subject line tester tool. Tools with positive reviews and favorable user experiences are prioritized.
- AI Capabilities: AI-powered insights provide a competitive edge in subject line optimization. Tools that leverage AI and data from past campaigns provide more personalized and accurate results and recommendations. We give preference to these tools.
Top 15 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. TestSubject by Zurb
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
Pros
- 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
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Use Zurb to preview how your email subject lines will appear on mobile phones and optimize them where necessary.
2. 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
Pricing
- Free
Tool Level
- Beginner/Intermediate
Usability
- Easy to use
Pro Tip: Integrate SubjectLine.com with ChatGPT and use it to create catchy and more effective subject lines.
3. 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
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Use personalized subject lines to create an instant connection with your audience.
4. 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
Pricing
- Free
Tool Level
- Intermediate/Expert
Usability
- Moderately easy to use
Pro Tip: You can use SendCheckIt to optimize more than just your subject lines; use its generative AI to improve your entire email creative workflow by miles.
5. 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 email marketing tool 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
Pricing
- Free
Tool Level
- Intermediate/Expert
Usability
- Moderately easy to use
Pro Tip: You can get in depth insights into what’s wrong with your email subject lines with Mizy. This will help you learn and adapt with time.
6. 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
Pricing
- Free
Tool Level
- Beginner/Intermediate
Usability
- Easy to use
Pro Tip: You can use Refine by Moosend to analyze your subject lines based on the number of subscribers you have and the specific Industry you operate in.
7. 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 headline 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
Pricing
- Free
Tool Level
- Intermediate/Expert
Usability
- Moderately easy to use
Pro Tip: Go one step further by using AMI’s copy analyzer to check for flaws in your email body and fix them.
8. 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
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Use Capitalize My Title’s Email Subject Line Tester to search for power words that can help you create more attention-grabbing subject lines.
9. Free Subject Line Tester by EmailTooltester
Image via EmailTooltester
The Free Subject Line Tester by EmailTooltester is a web-based tool that helps marketers optimize their email subject lines for better display.
You can have a real-time preview of how your suggested subject lines appear on various mobile devices in just a few seconds. This way, you can fine tune your subject line and email based on the preview to get more opens.
Key Features
- Character count display
- Mobile device preview including iPhone, iPad, Google Pixel, and Samsung Galaxy models
Pros
- It is free to use
- It allows real-time feedback
Cons
- Unlike other subject line tester tools, the features are limited to subject line preview
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Preview variations of your subject line based on lengths, word choices, exclamation points, and other elements to see which one catches the eye most effectively.
10. Email Subject Line Analyzer Tool by IsItWP
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 details and 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
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Use IsItWP’s Email Subject Line Analyzer to optimize the word count, character count, and emoji count of your subject lines.
11. 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, scannability, and reading level of your email’s content
Pricing
- Free with all Mailchimp packages, including the free one
Tool Level
- Beginner
Usability
- This subject line tester is easy to use
Pro Tip: Use IsItWP’s Email Subject Line Analyzer to optimize the word count, character count, and emoji count of your subject lines.
12. 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 also helps ensure 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 message 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.
- Analyzes headlines and email copy and gives suggestions to improve them.
- 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.
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: You can use Spam Check by Postmark to check all components of your email, including subject lines, full headers, and content.
13. 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.
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: Use Omnisend’s A/B testing feature to compare different variations of email subject lines and pick the one that performs best.
14. Mailmeteor
Image via Mailmeteor
Mailmeteor is an intuitive subject line tester that uses advanced AI algorithms to score your subject lines based on several criteria. It considers features like email length, number of question marks, exclamation marks, emojis, spam words, and much more.
This tool works so well as one of the best email subject line testers because it doesn’t just analyze your subject lines, but you can also generate powerful subject line ideas to choose from.
Let’s take a closer look at its key features.
Key Features
- AI email writer for generating compelling email copy
- Email permutator
- Instant email scoring
- Analyzes email copy and subject lines for spammy words that may affect deliverability
- Generative AI content writer that provides better email subject line suggestions
Pros
- Easy to use
- Generates instant results
Cons
- Limited integrations
Pricing
- Free
Tool Level
- Beginner to intermediate
Usability
- Easy to use
Pro Tip: Looking for a potential lead’s email address? Use Mailmeteor’s email permutator to find it.
15. 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.
With Mailshake, you don’t need to worry about creating email campaigns. It 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.
Pricing
- Free
Tool Level
- Beginner
Usability
- Easy to use
Pro Tip: You can make your emails easier to read by using Mailshake’s Email Copy Analyzer to find words that are difficult to read and replace them with easier ones.
FAQ
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-converting 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 subject 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:
- TestSubject by Zurb
- SubjectLine.com
- The #1 Email Subject Line Tester by CoSchedule
- SendCheckIt
- Mizy’s Free Email Subject Line Tester by Automizy
- Refine by Moosend
- Headline Analyzer by AMI
- Email Subject Line Tester by Capitalize My Title
- Free Subject Line Tester by EmailTooltester
- Email Subject Line Analyzer Tool by IsItWP
- 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.
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