subject line tester tools

Best 9 Email Subject Line Tester Tools You Can Use

In this article, you’ll find out which are the best email subject line tester tools you should be using.

We’ll talk about tools to test your subject line based on:

  • Engagement
  • Mobile and Desktop visibility
  • Spam Score
  • Deliverability
  • Readability

If you want to test your subject lines, you’ll find your next favorite tester below.

Let’s get started.

What is a Subject Line and Why is It Important?

A Subject Line is the topic of your email. It acts as an introduction to your email that lets the readers know what to expect. The subject line is the first thing your readers will see when the email lands in their inbox, and it should entice the reader to open the email.

So, how important is your subject line?


35% of users will open an email based on the subject line alone, and 69% of emails are sent to spam based exclusively in the subject line.

For anyone with a properly built email marketing campaign, a subject line is often the only factor between an email being opened or the sender being marked as spam, forever.

If you want to get opens and engaged users, you need to test your email and make sure your subject line is the best it can be.

Best Email Subject Line Tester Tools

Here are some of the best email subject line tester tools you can find:

Test Subject – Zurb

example 1

TestSubject is a simple and free online tool made by Zurb to show you how your subject line, sender name, and pre-header text will look to your readers.

Just copy and paste the text you want to test, and this tool will immediately show you how it’ll all look on the most popular email clients and mobile devices.

This is a great tool to visualize your customer experience when interacting with your emails, so you know exactly how much they’re reading.

Price: Free

Mizy – Automizy

free email subject line tester

Powered by the acclaimed Automizy’s AI, Mizy is another free email subject line tester. It tests your subject line against all emails that were sent from Automizy’s platform, so it can predict how well your subject line will do.

Once you enter your subject line, it’ll rate it from 0 to 100, giving you tips on how to improve your subject line to maximize your open rate. If you want to convince your readers to take an action (such as opening the email), take a look at these great CTA examples and adapt them to your headlines.

email marketing form

This tool is perfect if you’re looking for an analyzer tool that tests your subject lines not based on a to-do formula, but on actual, real campaign performance.

Price: Free

Headline Analyzer – CoSchedule

headline analyzer

The Headline Analyzer by CoSchedule tests your subject line based on your keywords, word balance, sentiment, and effectiveness. 

It’s a great tool to get an overall subject line ranking, although you will have to fill up your information before you get any results. However, it has great reviews, with one user noting how it helped him improve and use power words in his subject lines to increase open rates. 

If you want to use a free, highly-rated, multipurpose subject line tested, the Headline Analyzer is among the best options for you.

Price: Free

Spam Check – Postmark


If you’re having a large amount of emails being sent to spam, you should definitely use a spam tester, like Postmark’s Spam Check.

Spam Check tests not only your subject line, but your whole email to see how likely your message is to be categorized as spam by email servers. It will give you very basic information on why your message has the score it has, and how to improve it.

Although it only checks text and no images, this is a great tool if you’re looking for a simple, no-registration option to test all your emails before pressing the “Send” button.

Price: Free

Install SmartrMail Banner

Emotional Marketing Value Headline Analyzer

emotional marketing value headline analyzer

EMV stands for Emotional Marketing Value. EMV words make up 20% of the English language and appeal to the emotional and empathetic side of the brain.

If you want to use these powerful, emotion-inducing words, there’s no better option than the EMV headline analyzer.

This tool developed by the Advanced Marketing Institute tests your subject line to find out its EMV score. With it, you can establish a deeper, emotional connection with your reader to get them to open the email and check what’s inside.

It then tells you which emotion your headline inspires: Intellectual, Empathetic, or Spiritual. You can then determine if your headline is the right fit for your email, and read the tips to increase the sentiment you’re looking for.

You can use it to guarantee an emotional response when writing about your customer’s pain points.

Price: Free


touchstone line tester tool

Touchstone is an online subject line tester used to predict the impression and click and conversion rates based on your headline. It does this through a proprietary algorithm that’s so powerful, that its predicted performance is within 1-2% of the actual open rates.

This high-end tool is not for everyone. Although it is highly powerful and intelligent, it can also be expensive, so its use is probably better for professional marketing teams, and not for individuals. 

The more you pay, the more features you’ll get, like email reporting, filter options, tech support, and a lot of testing functionality.

This tool is especially useful to guarantee the deliverability of your cold emailing efforts, since your sales will directly be affected by open rates.

Price: Essential, $69; Expert, $99; Enterprise, $297. Free trial available

Email Subject Line Tester – Send Check It

send check it

The Email Subject Line Tester, by Send Check It, is a free and simple online headline tester. It tests your subject lines against over a dozen principles, showing you previews of your headline, and giving you an overall score.

This quick tool is great to find out the readability, sentiment, and scannability of your subject line. 

It also gives you great intel on spammy words and stylistic choices that you can use to improve your open rate.

Price: Free after registration.

IS Not Spam

is not spam filter

What it tests: If your email triggers common spam filters

Is Not Spam tests your email’s likelihood of triggering spam filters by having you actually send your email to them. Within a few minutes, Is Not Spam sends you a detailed report evaluating your copy, subject line, and HTML code. It tells you which spam filters your email didn’t pass and gives you valuable insight on how to avoid issues. 

With this platform, you can test your emails to check its SPF, Sender ID, DomainKeys, DKIM, and Spam-triggering factors.

This is a great tool to use if your deliverability has been going down, or if you want to avoid delivering to Spam inboxes when sending a particularly spam-looking email.

Price: Free

Hemingway App

subject line tester tool

The Hemingway App tests the readability of your headline and content to help you make your email as easy to read and scan as possible.

All you need to do is to paste a copy of your draft on the editor. It’ll then highlight common writing errors, complex and dense sentences, and lengthy content so you can improve your copy. You can use it to improve your favorite email templates and find and correct your content’s potential issues.

The Hemingway App also gives you useful tips to improve your writing and tailor it to your audience’s reading level.

If you don’t like Hemingway, there are several good Hemingway alternatives out there too:

  • ProWritingAid
  • LanguageTool
  • Grammarly
  • Ginger
  • WordStream
  • Ludwig Guru
  • Copywritely
  • Textmetrics
  • SEO Tagg
  • Evernote
  • Xtensio

Price: Free


Checking headlines for the best impact and deliverability is crucial, but let’s not forget that there’s no quick fix for deliverability. If you want a more long-term solution to this issue, you have to start at the core.

Fixing your email authentication step-by-step will lead your emails right into your recipients’ inboxes. SPF, DKIM, and DMARC protocol deployment is a steady course to improving your domain standing among internet service providers and trust toward outgoing emails on your business’s behalf.

EasyDMARC’s email authentication tools don’t require technical assistance and expert knowledge. Although the implementation takes time (depending on the size of your business, sending sources, and outgoing email volume), it protects your recipients from phishing and spoofing attacks.

In addition to deliverability improvement and avoiding phishing, email authentication deployment gives you visibility into the business email environment, control over your business identity, and adds to operations and communication security.


Your subject line can make the difference between your users clicking and reading through your email, and your users never even receiving your email to begin with.

With these tools, you’ll be able to avoid spam filters, cut out texts, and boring headlines. Start using them to write the best email subject lines today.

About Will Cannon: Previously known as the entrepreneur behind the lead generation company BWG, finding leads for companies like Dropbox, Morgan Stanley, ADP, and many other Fortune 500 companies, Will Cannon is currently the founder and CEO of UpLead.

Uplead is a B2B sales intelligence platform that helps companies identify their best-fit customers and reach out to them.

Scroll to Top